Case No: HT-02-227
Case No: HT-02-366
Neutral Citation No. [2003] EWHC 726 (TCC) 
IN THE HIGH COURT OF JUSTICE
QUEENS BENCH DIVISION
TECHNOLOGY AND CONSTRUCTION COURT

St. Dunstan’s House,
133-137, Fetter Lane,
London, EC4A 1HD

Date: 15 April 2003

B e f o r e :

HIS HONOUR JUDGE RICHARD SEYMOUR Q.C. 
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	 (1) MOIZ AHMED SIDDIQUI
(2) ISHRAT SIDDIQUI	
Claimants
	
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	 COUNCIL OF THE LONDON BOROUGH OF HILLINGDON

                  BHAJAN SINGH SOHANPAL

                                       -and-
COUNCIL OF THE LONDON BOROUGH OF HILLINGDON	
Defendant

Claimant

Defendant              	

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Robert Stokell (instructed by Merricks for the Claimants in the Siddiqui action and instructed by BPE for the Claimant in the Sohanpal action)
Timothy Lord (instructed by Vizards Wyeth for the Defendant in both actions)

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JUDGMENT: APPROVED BY THE COURT FOR HANDING DOWN (SUBJECT TO EDITORIAL CORRECTIONS)

H.H. Judge Richard Seymour Q. C.  : 
Introduction
1.	Laburnum Grove in Ruislip, Middlesex is a small development of residential properties undertaken in about 1980 or 1981 by a company called Matthew Homes Ltd. (“Matthew”). In this judgment I shall call that development “the Development”. The Development was constructed on the site (“the Site”) of a property formerly known as Bury Street Farm. It was common ground before me that the soil underlying the Site is predominantly London Clay. London Clay can include sand lenses, which are pockets of sand surrounded by clay. London Clay is susceptible to changes in volume as a result of the presence or absence of moisture. In laymen’s terms, it shrinks in the absence of moisture, but swells, if below its natural moisture content, if made wet. 
2.	The Development involved the construction of thirteen houses and associated garages on thirteen plots. A road called Laburnum Grove was constructed to afford access to each of the plots. That road is a cul-de-sac. The plots laid out for the purposes of the Development were numbered consecutively from the South-West corner of the Site in a curve towards the North-West, round to the North-East and then back towards the South-West. At the North-East side of the Site, abutting the North-East boundary, three plots were laid out, respectively numbered 8, 9 and 10. In this judgment I shall refer to those plots, respectively, as “Plot 8”, “Plot 9” and “Plot 10”. Upon Plot 9 were constructed a house, to which I shall refer in this judgment as “House 9”, and a garage, to which I shall refer in this judgment as “Garage 9”. Upon Plot 10 were constructed a house, to which I shall refer in this judgment as “House 10”, and a garage, to which I shall refer in this judgment as “Garage 10”.
3.	On the North-East side of Plot 8, Plot 9 and Plot 10 lay Ruislip Wood (“the Wood”). The Wood is an area of ancient woodland which has existed for many centuries. Its present extent is some 800 acres and it is apparently the largest area of unbroken woodland in London. The freehold owner of the Wood is the Council of the London Borough of Hillingdon (“the Council”).
4.	On the South-East Plot 10 abuts the curtilage of “The Plough” public house (“the Public House”).
5.	Mr. Moiz Siddiqui purchased Plot 9 in about October 1981 immediately after the construction of House 9 and Garage 9. He purchased the property in his sole name, but on 1 September 1982 he transferred the freehold title to his wife, Ishrat, and she remains the freehold owner of Plot 9.
6.	Mr. Bhajan Sohanpal purchased Plot 10 in 1986 and he is the freehold owner of that property.
7.	On a number of occasions over the years, starting in fact soon after Mr. and Mrs. Siddiqui moved into House 9, they noticed cracks in the structure. It will be necessary to consider the history of damage to House 9, and, indeed, to Garage 9, in some detail, but at this stage it is sufficient to record that on three occasions, respectively in 1988, 1992 and in 1999, significant work was undertaken with the aim of remedying the causes and symptoms of the apparent defects in House 9. The action brought by Mr. and Mrs. Siddiqui against the Council (“the Siddiqui Action”) was in respect of the works undertaken in 1999. In short what was said was that the necessity for the works undertaken in 1999 arose as a result of the action of the roots of oak trees in the Wood causing subsidence of the soil under House 9 and Garage 9 and consequent damage. That action of the trees roots was said to amount to a nuisance for which the Council was in law liable to Mr. and Mrs. Siddiqui.
8.	It does not appear that House 10 suffered from any structural problems until some time in 1995. However, damage was noticed in 1996 by Mr. Sohanpal and works were undertaken to remedy that damage in 1998. The cause of the damage which necessitated the undertaking of those works was again said to be the action of the roots of oak trees in the Wood resulting in subsidence of the soil under House 10. In the action brought by Mr. Sohanpal against the Council (“the Sohanpal Action”) Mr. Sohanpal sought recovery from the Council of the cost of the works undertaken in 1998, again on the ground that the alleged action of the tree roots was in law a nuisance for which the Council was responsible.
9.	Because of the possibility of common questions of fact arising in both the Siddiqui Action and the Sohanpal Action I ordered that the two actions should be tried together.
10.	The Council disputed liability both in the Siddiqui Action and in the Sohanpal Action. In essence it contended that the probable cause of the damage of which complaint was made in each case was heave of the underlying soil, not subsidence, and thus not the result of any encroachment of tree roots from the Wood. However, it was strongly urged upon me by Mr. Timothy Lord, who appeared on behalf of the Council, that it was not for the Council positively to prove any cause of any damage. Rather it was for the Claimants in each action to prove positively that the cause of the damage of which they respectively complained was the action of roots of trees in the Wood. In support of that submission, which seems to me to be self-evidently correct, Mr. Lord reminded me of the decision of the House of Lords in The Popi M [1985] 2 All ER 712, a case in which the issue was whether the sinking of a ship had been caused by a “peril of the seas”, and was thus covered by insurance. The only substantive speech was that of Lord Brandon of Oakbrook. At page 714E-G he said:-
“In approaching this question [whether the trial judge and the Court of Appeal had been justified in drawing the inference that the cause of the loss of the vessel was a peril of the seas] it is important that two matters should be borne constantly in mind. The first matter is that the burden of proving, on a balance of probabilities, that the ship was lost by perils of the seas is and remains throughout on the shipowners. Although it is open to the underwriters to suggest and seek to prove some other cause of loss, against which the ship was not insured, there is no obligation on them to do so. Moreover, if they chose to do so, there is no obligation on them to prove, even on a balance of probabilities, the truth of their alternative case.
The second matter is that it is always open to a court, even after the kind of prolonged inquiry with a mass of expert evidence which took place in this case, to conclude, at the end of the day, that the proximate cause of the ship’s loss, even on a balance of probabilities, remains in doubt, with the consequence that the shipowners have failed to discharge the burden of proof which lay on them.”
11.	It was also contended on behalf of the Council that, if the cause of the damage complained of in the Siddiqui Action or of that complained of in the Sohanpal Action was the action of roots of trees in the Wood, it was not reasonably foreseeable that the roots of the relevant trees would cause the damage. It was further contended that in any event the Council should have been afforded an opportunity in each case, which it was not, to abate the nuisance. I shall return to these contentions later in this judgment.
12.	Quantum was agreed, subject to liability, in both actions. In the Siddiqui Action the agreed cost of remedial works was £110,000, of which £200 - £300 was agreed to be referable to repairs to Garage 9, and it was agreed that a sum of £500 should be paid, if liability was established, in respect of general damages. In the Sohanpal Action the agreed cost of remedial works was £98,445, and again it was agreed that a sum of £500 should be paid, if liability was established, in respect of general damages.
The mechanisms of subsidence and heave
13.	It was common ground before me that in a case in which subsidence has been caused by the action of tree roots what happens is that tiny, hair-like roots growing out from, and usually at the end of, more substantial fibrous roots, extract moisture from the soil. As that happens a soil susceptible to alteration in volume as a result of the abstraction of water, such as London Clay, will shrink. That shrinkage will reduce the support which the soil provides to structures built upon it, and that reduction in support may cause the whole, or part, of the structure to sink. Differential sinking typically causes damage to a structure. As the whole process is dependent upon the abstraction of water by tree roots, in the case of deciduous trees it can only happen during the growing season. In Southern England the growing season is typically from about April to about September. The process of abstraction of water by tree roots, if it is to affect the stability of the soil as a support for structures, must cause a reduction in volume, which in a clay soil can occur by a reduction in moisture content – essentially drying out the soil. That process is technically called “desiccation”. Unless desiccation has occurred the cause of damage to a structure built upon a clay soil cannot be the extraction of water by tree roots.
14.	Heave is essentially the opposite of subsidence on a clay soil. It is the consequence of re-hydrating a desiccated soil. Thus for it to be the occasion of damage to a structure built upon the relevant soil, that soil must be desiccated at the time of construction. A typical cause of soil being desiccated at the time of construction is the removal of vegetation from a clay soil shortly before construction operations commence. The sources of water which can prompt re-hydration of a desiccated soil can be many and various. However, rainwater as such will, according to the evidence of Dr. Frank Hope given at the trial, which I accept, only affect the upper 50 centimetres to one metre of the ground. For re-hydration to occur at lower depths the source or sources of water must themselves be in the ground.
15.	As the degree of movement caused by subsidence or heave on a clay soil is often not very great in absolute terms, it is frequently not possible easily to detect whether a structure thought to have been damaged by one or the other has gone up or gone down. If it can be shown to have gone down, that must, in the type of case now under consideration, be as a result of subsidence. If it can be shown to have risen, that, conversely, must be as a result of heave.
16.	In the absence of evidence that a damaged structure had definitely sunk or definitely risen what, in simple terms, one would be looking for in any investigation of ground conditions in the context of damage thought to be caused either by subsidence or by heave was evidence of the absence of moisture from the soil. Lack of moisture in the ground indicates tree root action, and thus the possibility of subsidence, whereas no lack of moisture indicates that the cause of the damage cannot be subsidence, but might well be heave. As heave occurs as a soil which has been desiccated re-hydrates a degree of desiccation is not uniquely diagnostic of subsidence, but subsidence cannot occur without desiccation.
The history of the Site prior to the undertaking of the Development
17.	On 18 July 1969 the area of the Site was photographed from the air by Aerofilms Ltd. (“Aerofilms”). The relevant photograph was submitted to Mr. D. A. Simmons of Aerofilms, a chartered surveyor, for interpretation. His brief was to plot the locations of the trees shown on the photograph on a copy of an Ordnance Survey map which showed the Site after completion of the Development, and to estimate the heights of the trees shown. The accuracy of the work of Mr. Simmons was not in dispute before me. Mr. Simmons allocated to each tree which appeared in the photograph a number. I shall refer to the trees which are relevant for present purposes using the numbering adopted by Mr. Simmons.
18.	On Plot 9 there was, on 18 July 1969, one tree, Tree 39, the height of which was 1.8 metres. At the trial it seemed to be common ground that Tree 39 was probably an apple tree, as it was known that there had been an orchard on the Site, although in a different part of it. Tree 39 was within the footprint of House 9, meaning by that that it stood on soil now under House 9, towards the left hand side, viewed from the road, and midway between the front and the back of House 9.
19.	On Plot 10 there were five trees on 18 July 1969. Tree 38 was at the rear left hand corner of the footprint of House 10 and stood to a height of 5.1 metres. Tree 36 was just outside the footprint of House 10 at the rear right hand corner and stood to a height of 6.3 metres. Tree 35 was to the front right hand side of the footprint of House 10 and stood to a height of 4.9 metres. Tree 34 stood to the front, road, side of the footprint of Garage 10 to a height of 5.9 metres. The last tree within Plot 10 was Tree 37 which stood to the rear on the right hand side, viewed from the road, of the footprint of House 10, to a height of 7.1 metres.
20.	In the grounds of the Public House immediately to the rear North-East corner of the footprint of Garage 10 on 18 July 1969 was Tree 23. Tree 23 at that time stood to a height of 12.9 metres.
21.	In the Wood on the North-East side of Plot 9 on 18 July 1969 there were three trees adjacent to the boundary. Tree 41 stood almost at the point at which the boundary between Plot 9 and Plot 10 was later placed. It was 14.9 metres high. Not far from Tree 41, moving in a North-North-Westerly direction, was Tree 42, which stood to a height of 17.7 metres. Continuing in the same direction, but further away from the boundary with the Site, was Tree 43, the height of which was 19.1 metres.
22.	To the North-East of Plot 10 on 18 July 1969 Tree 40 stood in the Wood to a height of 14 metres.
23.	The trees on Plot 9 and Plot 10 were all removed at some point prior to the commencement of the Development.
24.	In advance of the commencement of the Development a Mr. Jon Chamberlain was commissioned to undertake a soil investigation upon the Site. He dug three trial pits, the locations of which were shown on a rather crude sketch which was put in evidence. Doing the best one can, the nearest trial pit to Plot 9 and Plot 10 was Trial Pit 2, which seems to have been dug approximately in the subsequent location of Plot 8. Mr. Chamberlain compiled logs of each of the trial pits which he dug. The log of Trial Pit 2 indicated that it was dug on 6 December 1979 to a depth of 1.3 metres, at which point, so it was recorded, “Hole stopped because clay too stiff to penetrate with hand auger”. At that point, so Mr. Chamberlain wrote in the log, the pit was, “Dry”. The other recorded observations in the trial pit were that the depth of topsoil was 0.25 metres, beneath which was “Orange clay becoming stiff brown clay”. Mr. Lord urged me to interpret the log of Trial Pit 2 dug by Mr. Chamberlain as indicating that the clay at 1.3 metres depth was dry, that is to say, desiccated, both because of the reference to the bottom of the pit being “Dry” and because, so he submitted, the fact that the soil was too stiff to penetrate indicated that it was hard, and therefore dry, clay. I accept that submission. If the soil had been stiff because it was well-hydrated the bottom of the pit would not have been dry. Mr. Robert Stokell, who appeared on behalf of the Claimants in both actions, submitted that I should treat with considerable circumspection the written records of any ground investigations not undertaken specifically in the context of the works the costs of which are claimed in these actions because one did not know anything about the skill or competence of those undertaking those investigations. That is a fair point so far as it goes, but it seems to me, given the limited information put before me and before the expert witnesses in these actions, that it would not be appropriate simply to disregard any piece of evidence which is available. Rather I should consider it along with the totality of the other evidence. Moreover, in the absence of any specific reason to doubt the skill and competence of someone undertaking soil investigations at the Site or on Plot 9 or Plot 10, it seems to me that I should proceed on the basis that whoever undertook a particular investigation was setting out to do it properly and was viewed by those who entrusted the task to him or her as apparently competent to do it.
25.	Matthew seems to have commissioned a firm of structural engineers, Messrs. Marks, Heeley and Brothwell (“MHB”) to give advice concerning the design of the foundations for the houses to be constructed on the plots into which the Site was to be divided for the purposes of the Development. The recommendations of MHB were set out in a document dated 17 June 1980 and  entitled “Bury Street Farm Ruislip Recommendations on Foundation Design”, of which a copy was put in evidence. That document included the following:-
“4.2 On the line of the south [word illegible] boundary approximately mid-way along its length, there is a willow tree. Further along this boundary line in the north east corner of the site there are two oak trees.
4.3 Outside the north east boundary there is a wood comprising various mature trees….
6.5 Plots 8 and 9
Further trial pits are to be undertaken to establish root growth. Foundations could be 2.0 metres deep.
6.6 Plots 10, 11, 12 and 13
The trees are extremely close to these properties. Consequently, very deep footings or perhaps short bored piles should be used.”
26.	Mr. Lord submitted that the terms of paragraphs 4.2 and 4.3 of the document from which I have quoted in the preceding paragraph were evidence that two of the trees shown on the aerial photograph taken on 18 July 1969 as standing within the boundaries of what became Plot 10 were oak trees. Mr. Stokell contested that submission, asserting that the reference in paragraph 4.2 was more, or at any rate equally, consistent with the reference being to trees in the Wood. I accept the submission of Mr. Lord on this point. It seems to me that there is a plain contrast between paragraph 4.3, which was in terms concerned with trees in the Wood, and paragraph 4.2, which was concerned with trees along the boundaries of the Site, but within those boundaries.
27.	There was put in evidence a copy of a letter dated 19 June 1980 written by MHB to Matthew which included this reference:-
“The three boreholes to the north east of the site indicate that the foundations in this area should be as follows.
Plots 8 and 9
At rear 2 metres deep. Remainder 1.8 metres deep.
Plots 10 and 11
2 metres deep.”
Mr. Stokell submitted that I should interpret the reference to three boreholes as indicating that ground investigation in addition to that of Mr. Chamberlain had by the date of the letter been undertaken in the North-East of the Site. That seems to me to be an appropriate conclusion. However, no evidence was led before me as to the locations of any such boreholes, the depths to which they were sunk, or what was found. Consequently a finding that such boreholes had been sunk does not really advance my consideration of the issues which I have to determine in these actions.
28.	Mr. George Mist, who on the day he appeared in the witness box was to retire as the Council’s Chief Ranger after 30 years service in that role, gave evidence that before the commencement of the Development the Site was very overgrown and derelict. That evidence was not contested and I accept it. In the light of it I conclude, contrary to the submission of Mr. Stokell that there was no evidence as to when any of the trees shown on the aerial photograph taken on 18 July 1969 as then existing on what was to become Plot 9 or Plot 10 were removed, that the relevant trees were not removed until shortly before, and for the purposes of facilitating, the Development. 
The foundations of House 9 and House 10 as constructed
29.	It was not, I think, in dispute, that, as originally constructed, the foundations of House 9 were sunk to a depth of 2.3 metres, or thereabouts, along the rear wall and for a short distance at each of the returns of the rear wall, with the remaining foundations being taken to a depth of 2 metres.
30.	The foundations of House 10 were taken to a uniform depth of 2.3 metres.
31.	There was put in evidence a note of an inspection made of the construction of the foundations of Plot 9 on 3 September 1980 by the Council’s building inspector. For what it is worth, which in my judgment is not much, the note recorded that it had not been possible to enter the foundation trench because it was unstable, but from ground level no tree roots had been observed within 300 millimetres of the bottom of the trench. A similar note was made in relation to the foundation trench of House 10 based on an inspection on 10 September 1980.
Damage to House 9 in 1987
32.	Mr. Siddiqui made a statement dated 24 February 2003 for the purposes of the Siddiqui Action. The accuracy of the evidence given in the statement was not contested and Mr. Siddiqui did not attend the trial to give evidence in person. His witness statement included these passages:-
“4. We first noticed minor cracks in the property in the months following our moving in. At first we thought these were simply due to normal settlement, but during the following years, further and more serious cracks appeared until in June 1987 these seemed so much more serious that we contacted the developer, Matthew Homes Limited and the NHBC. The NHBC sent engineers to investigate, and they advised that the cause of the damage was subsidence, and that we should notify our buildings insurers. We accordingly did. We also instructed our own engineers, Sinclair Johnston to carry out further investigations.
5. Our insurance company’s loss adjuster, Barry Breed of McLarens, visited the site as well, and the damage at the time of this and the other two claims is recorded in his reports and in the reports of Sinclair Johnston. I recall that the worst cracks at this time were in the kitchen and lounge areas. 
6. The house had to be underpinned and we had to move out into rented accommodation for about two months in about October to December 1988…”
The kitchen of House 9 is on the left-hand side at the rear, as viewed from the road. The “lounge”, if that is intended as a reference to what on a plan of House 9 put in evidence was called a “living” room, is on the right-hand side at the front.
33.	There were put in evidence the logs of two trial holes dug by National House-Building Council (“NHBC”) immediately outside the footprint of House 9 on 19 November 1987. Trial hole 1 was at the rear right-hand corner of House 9, viewed from the road. It was sunk to a depth of 3.55 metres. The log recorded that fill had been found to a depth of 0.9 metres, then down to a depth of 2.56 metres the ground was described as, “Brown London Clay with grey inclusions, odd traces of sand small roots present throughout bore”. Between a depth of 3.05 metres and the bottom of the trial hole the ground was described as, “very firm brown London clay with numerous selenite crystals, clay moist with odd pieces of decayed wood”.  Trial hole 2 was dug at the rear left hand corner of House 9 and was continued as a borehole to a depth of 3.55 metres. The record of what was found was, “Throughout bore was brown London clay which was moist (no signs of any roots)”.
34.	As part of the investigations at this time Messrs. Michael Gallie & Partners (“Gallie”) were instructed to prepare a level survey of House 9. A plan showing the levels as measured was put in evidence. I shall return to the possible significance of that level survey. According to a letter dated 25 March 1988 written by Messrs. Sinclair Johnston (“Sinclairs”) to Mr. Breed of McLarens, of which a copy was put in evidence, at the time the significance of the level survey was thought to be that it showed that the rear right-hand corner of House 9 had settled relative to the rest of the house. The letter included this passage:-
“While we have discussed the NHBC investigation before, it is, I believe worth recording Mr. Hughes remarks:-
1. One trial hole was sunk at the rear right hand corner. This proved the dept [sic] of the existing foundation at 2.45mm [sic – presumably metres was meant]. Auger holes were taken down from 300mm above founding level. Firm brown clay with traces of fine roots were noted. The roots were not tested for sap (ie, alive or dead), or for species identification. This is because they were so fine.
2. A level survey was carried out which confirmed that the rear right hand corner had settled about 20mm relative to the rest of the house.
3. A verticality survey was carried out which showed various out-of-plumb of the walls, particularly the rear left hand corner but which did not tie up with any particular pattern of movement.
4. Mr. Hughes could not identify and [sic] signs of heave in the property, the cracks in the flank wall clearly indicating settlement here.
5. Samples of clay from the auger holes were tested for moisture content but did not indicate any exceptional level of desiccation.
These points 1, 2, 3 & 4 agree with our own findings except that we did not receive any roots. …
We conclude that the clay soil to the rear of the site has suffered some moisture extraction and shrinkage relative to the front of the house, despite the depth of the foundations as installed. ”
35.	Three boreholes were sunk by Anchor Foundations Ltd. (“Anchor”) on 11 May 1988 for the purpose of providing information to assist in the design of underpinning for the rear of House 9. Copies of the logs of those boreholes were put in evidence. For present purposes it is only material to record that the logs did not indicate that any roots had been found below the level of a depth of  3.2 metres in any of the locations tested. Soil samples from the boreholes were sent for testing by Eastern Soil Search Ltd. (“Eastern”). A report on those tests was given by a letter dated 8 June 1988 written by Eastern to Anchor. The only part of that report which is material for present purposes was a comment that, “A slight moisture deficiency may be present at 1.00 metres depth at Borehole 3”. The results of the ground investigation were considered in an internal memorandum written by Mr. E. S. Hunt of McLarens to Mr. Breed. The context of the consideration was whether it might be possible for Mrs. Siddiqui’s insurers to make a recovery in respect of their expenditure in underpinning the rear of House 9. The memorandum included:-
“I have now had an opportunity to consider the results of the site investigation and agree with you that these are a little disappointing in as much as they show little or no moisture deficit, apart from a slight desiccation at approximately 1m depth in the borehole to the rear right-hand corner.”
36.	Mr. Breed of McLarens did write a letter dated 1 August 1988 to the Council. What he said was:-
“We are currently acting on behalf of GRE (UK) Ltd, the building Insurers of the above in connection with a claim submitted for subsidence/heave damage. The dwelling forms part of a development know as Bury Street Farm for which an application for planning permission was submitted dated 9th January 1979 to Hillingdon under Town and Country Planning Act 1971. The Local Authority reference was 15911/79/38. The applicant for planning permission was Matthew Homes Ltd and we enclose a copy of our letter addressed to them of even date from which you will note that weare [sic] holding them responsible for our Principal’s outlays. In view of your own potential liability in this matter we must formally write to you placing you on notice of our intent to seek recovery of costs. We enclose copies of relevant engineers reports, results of site investigations, recommendations etc. We would like to provide you with the opportunity of carrying out further inspections/investigations once repairs are under way and would suggest that any such visit on your behalf should be arranged in conjunction with Messrs. Sinclair Johnston, Consulting Engineers and/or ourselves.”
It does not appear that the Council acknowledged receipt of that letter or took any action in consequence of receipt of it. Equally it does not seem that McLarens or anyone else on behalf of Mr. or Mrs. Siddiqui sought to pursue the matter with the Council at this stage.
37.	The underpinning scheme adopted in 1988 for House 9 involved underpinning to a depth of 3.9 metres along the rear wall of the house, with a continuation at the returns for a short distance on the left and a rather longer distance on the right. Mr. Breed attended the site during the undertaking of the work as he was supervising it on behalf of McLarens. He was called to give evidence at the trial before me. He said that he looked into the trench in which the new foundations were to be constructed. He did not see any roots at a depth below 3.2 metres. He was satisfied that the underpinning work had been undertaken satisfactorily and the underpinning appeared to him to provide an adequate foundation. I accept that evidence.
38.	In August 1988 three further trial pits were dug at Plot 9. Sinclairs made a note in relation to a site visit on 15 August 1988. According to that note, in Trial Pit 1 some fine roots were found at a depth of 3 metres, in Trial Pit 2 no roots were found below the level of the existing foundations, while in Trial Pit 3 some fine roots were found at an unspecified depth. The roots found were sent to the well-known testing house, Richardson’s Botanical Investigations (“Richardsons”). In a letter dated 12 September 1988 Richardsons reported:-
“The roots you submitted in relation to the above on 16-AUG-88 and on 19-AUG-88 have been examined microscopically for identification by comparative anatomical methods. Their structure resembled most closely that of our reference specimens of roots of QUERCUS (Oak) and CASTANEA (Sweet Chestnut).
They were all similar, and the reason for the alternatives given above is that when small, these two types of root can be indistinguishable from each other. Only one root (the largest) from each of the 4 samples was examined in detail, but the remainder appeared similar under low magnification.
The Iodine test was positive (ie the root was recently alive when removed from the soil) only for a root from Pit 3, 3m deep, but the test is not very conclusive on very thin roots, so that I have not got absolute confirmation that the others were dead. [The iodine test is a test for starch, which is stored in some cells of living tree roots, but which is more or less rapidly broken down by micro-organisms upon the death of a root in the soil.].”
Damage to House 9 in 1991
39.	In a letter dated 2 April 1991 to McLarens Mr. Siddiqui reported that:-
“Further to my subsidence claim, if you recall back, there were signs of subsidence in the Hallway around the front door. At the time, it was decided not to do any under-pinning. Simply cracks were filled.
Serious cracks have now reappeared in the hallway to the extent of approximately half a centimetre and ceiling is disintegrating from the wall.”
40.	An organisation called Engineering Services for Insurers (“ESI”) was engaged to investigate. ESI reported on the results of a visual inspection of House 9 in a letter dated 3 July 1991 to Mr. Siddiqui, of which a copy was put in evidence. The letter included:-
“Report on Present Distress
It is understood that within a matter of weeks, probably during the summer of 1989, you detected signs of previous cracking within the building, which became progressively worse to a point where you instructed us to re-examine the property.”
That record was agreed for the purposes of the trial before me to be accurate.
41.	Mr. Siddiqui again instructed Sinclairs to advise. Site notes made by that firm on 3 October 1991 recorded the following damage:-
“1. Paving at rear badly ruptured – backfill has settled.
2. Kitchen – crack at junction of ceiling and rear wall over sink.
3. Kitchen/dinning [sic] room – crack in partition.
4. Dining Room – crack at junction of partition and rear wall.
5. Hallway/Front Room – crack over doorway in partition – 8mm.
6. Dining Room/Front Room - slight cracking over doorway – front room end of lintel defined.
7. Upstairs front room over hall – partition cracked abutting front wall, crack 2 mm at floor diminished towards ceiling.
-	fine raking crack in flank wall (in cupboard over stairs)
8. Stairwell – fine crack in flank wall below window.
9. Right hand flank wall – stepped crack about 2mm – from head of rearmost ground floor window to all of first floor window. 
10. Front right hand ground floor window – stepped crack – three courses.”
42.	Mr. Breed wrote to the Council about the new damage to House 9 in a letter dated 7 October 1991. That letter included:-
“The rear garden of 9 Laburnum Grove immediately adjoins an area of mature woodland which we believe is known locally as Ruislip Woods, just to the south of Ruislip Leado [sic]. The trees which are mainly oak are within a metres [sic] of the rear elevation of No 9 Laburnum Grove.
It is evident that the presence of the trees was taken into consideration when the houses was [sic] originally built as the trench fill foundations were taken down to a depth of approximately 2.4 metres. Accordingly [sic] to our information, Mr. Siddiqui first noticed the appearance of minor cracks in the property shortly after taking up ownership/occupation in 1981 but these were initially considered attributable to normal settlement/shrinkage problems. Further cracks appeared during 1986 although it was not until June 1987 that Mr. Siddiqui became concerned at the degree of movement which was taking place. Messrs. Sinclair Johnston carried out various site investigations which lead [sic] them to the conclusion that the rear half of the problem [sic] was suffering from the effects of subsidence. Insurers subsequently accepted a scheme for partial underpinning of the property whereby the existing foundations were taken down to 3.9 metres incorporating anti heave measures on the inner and outer face of the underpinning. The repairs which were carried out under the supervision of Sinclair Johnston were completed in August 1989.
More recently Mr. Siddiqui has noticed the appearance of further cracks in the property and has called Messrs. Sinclair Johnston back to advise. We have recently held a meeting on site to discuss what further investigations are necessary. During the course of our discussions it was suggested that we contact yourselves as we understand you have responsibility for the adjoining area of woodland and also gave approval for the Berry [sic] Street Development in 1979. In view of the close proximity of the trees to the rear of the property the engineers have suggested that we contact you to seek your co-operation with regard to reducing the height of the trees and keeping them in a reduced state in order to restrict their demands for moisture from the shrinkable clay subsoil.
We shall let you have further details in due course but in the meantime would appreciate acknowledgement of our letter and confirmation of your responsibility for the woodland.” 
43.	In a letter dated 7 October 1991 to Mr. Breed of McLarens Sinclairs expressed the initial view that, “The key movement, the subsidence and rotational movement of the front wall where it abutts [sic] the partition to the hallway measures as much as 8mm.” In the same letter the possibility of the cause of the damage then being experienced being heave was dismissed. However, in a letter dated 22 October 1991 to Mr. Breed Sinclairs expressed the view, following inspection of a trial pit, that, “the present damage is caused by an element of heave by increased volume of the clay subsoil under the main body of house.” Various further investigations were recommended, including a survey of the drains serving House 9 and the fixing of crack monitors. Of significance so far as the matters which I have to decide are concerned is that one of the further investigations recommended was the excavation of further trial pits, this time by R. M. Brown Foundations Investigations Limited (“Brown”). It does not appear that any further trial pits were in fact dug at this stage, but Brown did undertake ground investigations later, in 1998, and I shall come to the matters revealed by those investigations.
44.	Although the Council did not reply to the letter from Mr. Breed dated 7 October 1991, it did, in January 1992 cause some trees in the Wood to be pruned. It did not do any other work on any of the trees relevant to these actions between that time and 1998.
45.	It seems that the damage sustained by House 9 in 1991 was dealt with by repairs to the structure and decorations, with no further underground work.
Damage to House 9 and Garage 9 in 1997
46.	Mr. Siddiqui noticed yet further damage to House 9 in about August 1997. Once more he consulted Sinclairs. They undertook an inspection of House 9 on 11 September 1997 and prepared a record of what they then found. The record was:-
“1. Front elevation, right hand ground floor window, stepped crack about 1mm running down and to a hair crack just above inset course.
2. Same window, crack running up about 1mm, stepped crack towards the first floor window and fading out.
3. Ground floor window just to the right of the entrance porch, stepped crack running down from centre of this window about 1mm fading out to nothing.
4. Above same window above left hand corner, vertical crack about ½ mm running up and fading out at the string course.
5. Left hand flank wall, front portion, no defects. Side window to kitchen, in front of kitchen door, stepped crack running up about 1mm and fading out. Side door to kitchen no comment.
6. Main rear wall, small window to kitchen, fine crack above.
7. Double doors to kitchen, just able to distinguish raked pointing from previous repairs and slight cracking about ½ mm above double doors to dining room.
8. Below kitchen window stepped cracking running down on the line of previous repair.
9. Right hand flank wall previous patch repairs just distinguishable from original, both at high level running up to the small window and at low level to rear right corner, but no further cracking.
10. Small window to dining room further back of the two; slight cracking running down to the ground partly on the line of previous repair…
11. Outside the rear wall paving very disrupted and has settled although this has been relaid previously…
12. Small dwarf wall its brick courses ruptured about 10 – 15 mm, …
13. Side door to garage the rear part has moved back about 10mm giving stepped crack above and so that the door does not close. Similar amount of movement below the door frame…
14. Ground floor hallway, the partition to the right door to living room, vertical crack about ½ mm half way between the door frame and front wall and above the door frame 3 fine hair cracks and opening of the junction of the architrave.
15. Within ground floor front right living room vertical cracking forward of the door, outlining the previous repairs. Two fine cracks above the door and opening of the architrave.
16. Same room, door to the dining room and to the left cracking up to about 2mm raking back from left hand side of the door, … To the right of the door running towards the right hand wall, horizontal cracking in three extensions running towards the right hand wall about 50mm below the top of the door frame.
17. Also further about a metre to the left of this door, diagonal raking crack, hair crack to ½ mm in the plaster.
18. Within the dining room viewing door to the front sitting room, … same pattern and crack to the right of this door viewed from the back or left viewed from the front up to about 2mm. Horizontal cracking likewise.
19. On the right flank wall and dining room, window to the wall is boarded out with TG&V boarding but at ceiling level gap of about 1 – 2mm in the coving.
20. In this dining room the floor is uneven and to be investigated.
21. Kitchen rear left corner, staining in the ceiling from the shower above and cracking between the ceiling and the rear left flank wall. Kitchen work surface not level.
22. Downstairs WC under stairs no comment although slight cracking between the tiling and the ceiling which is the soffit for the stairs.
23. Stairwell; very slight horizontal lipping on plaster; downstairs window.
24. At top of stairs just possible to read previous repairs running up from top of stairs to cill of first floor window and left flank wall.
25. First floor front left bedroom, slight cracking between the ceiling and the front wall and between the window cill board and the window frame. In this room within the built in cupboard, stepped crack on the remote face which is block partition, outline of blockwork on the external wall.
26. In the left hand corner fine cracking between partition; i.e. plasterboard partition between this room and right hand room and in the right hand corner of this bedroom a gap previously filled between the junction of the skirting board.
27. Small middle room to the front, fine crack below window left hand side, viewed from the inside, cracking at the junction of the partition to the left and right hand bedroom particularly giving rise to gaps at the skirting. To the left of the window viewed from inside a crack running round to outline the end of the lintel and fading out to the ceiling and slight cracking between the ceiling and the front wall.
28. Front right hand room cracking between the ceiling and the front wall and again cracking when viewed from inside running up from left hand corner of the window outlining the end of the lintel and vertical cracking at the junction of the front wall and right flank wall.
29. Below the window partly concealed behind the radiator vertical crack about 1mm running down to the skirting board. Crack between the ceiling and the right hand flank wall which increases from the back towards the front right corner.
30. Rear right corner of this room crack between cross partition and right flank wall.
31. Rear right bedroom; cracking between the cross partition (to the front room) within the wardrobe; and the right hand flank wall about 3mm, and has ruptured the plaster at ceiling level.
32. Rear right room, rear right window left hand vertical crack running down to the skirting.
33. Rear left corner bathroom, shower tray in the corner.
34. Bedroom vertical crack obviously junction of plasterboard sheet on left wall to bathroom about ½ m back from front wall of bedroom here.
35. Rear central bathroom against left flank wall a partition abutts [sic] left flank wall vertical cracking increasing downwards to top of boxing out for cistern.
36. Stepped crack 1mm in the two brick courses below the front door.
37. In the dining room the floor uneven with dipped at the door from the dining room, the living room as commensurate with the cracking above the door and gap below the skirting board and floor in the front right corner of the dining room.
38. Mrs Siddiqui said the house was decorated previous July, ie 1996.
39. Row of dominant oak trees in park beyond fence ..”
47.	Mr. J. S. Johnston of Sinclairs sent a copy of the record set out in the preceding paragraph to Mr. Breed under cover of a letter dated 19 September 1997 in which he wrote, so far as is presently material:-
“1. At the rear of the building, there is a very significant fracture about 10mm above the side door of the garage. This is a result of the foundations of the rear wall of the garage having moved an equivalent amount.
The paving along the back of the house above the area of the previous underpinning again has settled.
The dwarf retaining wall beyond the rear right-hand corner of the house has moved and fractured about 10mm.
Considering the nature of the clay subsoil and the row of very substantial oak trees just beyond the garden fence nearby, such obvious distress in these external works is, while unfortunate, is [sic] understandable. The foundations to the garage and dwarf garden walls will not provide protection against subsidence in dry weather on very highly shrinkable clay with a large tree population adjacent.
2. The perimeter cavity walls of the building, face brick outside, plastered blockwork inside, exhibit slight but widespread cracking at many locations. On its own, without any other aspects, such cracking would be a cause for concern. In a house of this age, where any initial shrinkage, settling down etc. had taken place. It is worth noting that where previous repairs were carried out, there is no further movement or just very slight shrinkage cracking between the new mortar and brickwork.
3. Internally, there is around the perimeter of the building, the sort of cracking that occurs between plasterboard ceiling and perimeter walls, and along the front wall for example between plasterboard partitions built off timber floors and perimeter walls, and while annoying, is generally part of the characteristic of this type of building. In the first floor, right-hand room, this cracking is more defined.
4. What is exceptional however, is further cracking in the internal partitions. 
In the partition between the hallway and the main front right-hand living room there is clear cracking above the doorway, not exactly identical but similar in location and pattern to that previously occurred.
Again on the doorway between this living room and the rear right-hand corner, the dining room; is very significant cracking, up to 3-4mm above the doorway, and clear through the partition visible on both sides. This is clearly illustrated on the photographs. This internal cracking, particularly that between the living room and the dining room, is clearly not plaster shrinkage or anything of that nature, but is due to ground movement in some form.
Without further detailed investigation, I can only assume that there must be clay shrinkage in some way within the centre of the building.”
48.	Mr. Breed wrote once more to the Council on 12 January 1998. He set out the history of his principal’s dealings  with Plot 9 and with the Council, and concluded:-
“We would advise that despite our letters, meeting on site, various telephone calls etc. we have never received any formal written communication from yourselves and it would now seem evident that no further action has been taken on the trees as can be seen from the attached photographs. The trees have been allowed to grow without control over the past five/six years and we believe they are probably the major factor in causation of recent damage. We shall advise you further once in receipt of the engineers report but in the meantime should be obliged if you would notify your public liability insurers accordingly.”
This time there was a response to that letter. It was acknowledged by Mr. Harrison, Building Control Manager, in a letter dated 14 January 1998.
49.	Investigations undertaken at Plot 9 in 1998 included the sinking of boreholes by Brown and the fixing of crack monitors by a company called Avongard Ltd. (“Avongard”). It was common ground before me that the crack monitoring showed little of value, because readings were only taken twice, on 26 February 1998 and on 21 September 1998. Although each crack monitored widened somewhat, as the monitors were placed before the annual growing season for deciduous trees in Southern England began, but at a time when, if soil was re-hydrating, one would expect that process to be active, it was impossible to draw any sensible conclusion as to the cause of the widening of the cracks monitored. 
50.	Brown sank three boreholes on Plot 9 on 26 February 1998. Boreholes 1 and 2 were each sunk from the bottom of a trial pit. Trial Pit 1 was dug at the rear right-hand corner of Garage 9, as viewed from the road. Trial Pit 2 was dug in the front right-hand corner of the dining room of House 9, that is to say, midway along the right-hand wall of House 9 as viewed from the road, but inside the footprint of the house. Logs of the boreholes were put in evidence. 
51.	The log of Trial Pit 1 showed that the pit was dug to a depth of 1850 millimetres. Roots of live appearance with a diameter of up to 7 millimetres were noted down to a depth of 1500 millimetres, with roots of live appearance with a diameter of up to 3 millimetres from that depth down to the bottom of the pit. In Borehole 1, sunk from Trial Pit 1, hair and fibrous roots were noted to a depth of 3.6 metres. The borehole was taken to a depth of 5 metres and was noted as dry at the bottom. A number of samples of roots from Trial Pit 1 were sent to Richardsons for identification and testing. In a report dated 14 March 1998 Richardsons identified one root sample as oak and as having been alive shortly before being removed from the soil. They said that the other 27 root samples appeared to be similar.
52.	Trial Pit 2 was dug to a depth of 1.4 metres, which did not take it below foundation depth. Borehole 2 was sunk from Trial Pit 2 to a depth of 5 metres. Slight water seepage was noted at 3.4 metres depth and the borehole was noted as moist at the base. Below the level of 1.4 metres depth roots of dead appearance with a diameter of up to 2 millimetres were noted to a depth of 1.8 metres, roots of up to 1 millimetre in diameter were noted below that down to a depth of 2.5 metres, and hair and fibrous roots were noted below a depth of 2.5 metres down to a depth of 3.2 metres.
53.	Borehole 3, in the front garden on the left-hand side viewed from the road and approximately in front of the front door, was taken to a depth of 5 metres. Hair and fibrous roots were noted to a depth of 1.7 metres. The clay between 0.7 metres and 1.5 metres was noted to be moist, as was the clay between 4.7 metres depth and the bottom of the bore. The borehole log noted that, “Slight water seepage at 4.7m below ground level. Borehole moist at base and open on completion.” 
54.	In a letter dated 21 April 1998 to McLarens Mr. Colin Chambers, the Council’s Trees and Woodlands Officer, indicated that he would cause works to be carried out to trees in the Wood on an “entirely without prejudice basis”.  Those works, which were actually carried out, included removal of an oak tree which he identified on a plan of proposed works as Tree C, but which did not appear to be in the position of a tree shown on the aerial photograph taken on 18 July 1969, removing the lowest two limbs and reducing by 50% the crown of an oak tree which he identified as Tree G, which seems to be Tree 42, the removal of an oak tree which he identified as Tree H, which seems to be Tree 41, and the reduction of a hornbeam, which he identified as Tree I, but which seems to be Tree 40, so that both stems were the same height. A hornbeam which Mr. Chambers identified as Tree F and in respect of which he proposed to take no action, seems to be Tree 43. Mr. Chambers noted on his plan as Tree L what in fact was Tree 23. He recorded Tree L as privately owned.
55.	In the event, in order to deal with the damage which manifested itself in 1997 House 9 was fully underpinned by means of a piled raft. Garage 9 was not underpinned as the expense was not considered justified by the benefits which would be derived from that course. In the context of the remedial work a level survey of both House 9 and Garage 9 was undertaken by Messrs. Gryphon Surveys (“Gryphon”), to the significance of which I shall return.
Damage to House 10 in 1995
56.	It does not appear that any structural problems with House 10 were noted until 1995. Mr. Sohanpal submitted a claim to his buildings insurers in a claim form dated 8 September 1996, of which a copy was put in evidence. The damage as described in the claim form was, “Number of major cracks have been appeared [sic] in living room, bedroom, kitchen walls and floors”. That damage was said to have occurred “Last winter” and to have been discovered “2 months ago”. In his witness statement prepared for the purposes of the Sohanpal Action Mr. Sohanpal said, at paragraph 4:-
“I cannot recall the precise date when I first noticed some cracking in the living room wall and ceiling. I think it was early summer of 1996. The cracking was in the mortar and did not appear to be anything to concern myself about. However, by late summer (August/September 1996) I noticed that the cracking seemed to be very much wider and was present not only in the living room but also in the kitchen and a bedroom above. Indeed one day there was a loud cracking sound which I heard and which gave rise to the cracks in the ceiling of the living room.”
Some significance was sought to be attached at the trial to precisely when Mr. Sohanpal noticed damage in House 10. Mr. Stokell seemed anxious to afford Mr. Sohanpal every opportunity to say that it was in August or September of the relevant year, and that that was what he meant when he said in the insurance claim form that the damage had occurred “last winter”. Mr. Sohanpal did succumb to the temptation put in his path at one point. However, I do not accept that he was right to do so. By no stretch of the imagination as a matter of ordinary usage of the English language does either of the months of August or September fall within the winter. It was plain from the terms of paragraph 4 of his witness statement that Mr. Sohanpal does not now have any very definite recollection of exactly when he noticed what he considered to be significant damage to House 10. His statement seems to indicate a date one year after that which the claim form shows was correct on any view. I prefer the evidence of the claim form to Mr. Sohanpal’s current recollection of the date as at which he considered significant damage to House 10 occurred.
57.	Although McLarens were involved with the case of Mr. Sohanpal, as in the case of Mr. and Mrs. Siddiqui, as loss adjusters, this time it was a different office and the person concerned was not Mr. Breed, but Mr. Stephen Coates. He wrote a letter dated 8 February 1997 to the Council in which he said:-
“We are Chartered Loss Adjusters acting on behalf of Norwich Union Fire Insurance Society Limited, the interested property insurers in the above connection.
We are currently dealing with a potential subsidence claim at this property and understand that you own and control the adjacent areas of woodland in this area.
In order for our Principals liability to be established in this claim, we require copies of the official and approved detailed design and drawings, with particular reference to the foundation design and, also, tree clearance works undertaken to allow for the construction of properties in this area. 
We understand the property was constructed in 1982 and would request details as to Building Regulations approval for the property.
We would request your urgent attention to this matter and look forward to receiving the necessary information in the near future. 
In the meantime, if you should have any queries or comments, then please do not hesitate to contact Mr. Coates on the above number.”
The Council replied to that letter in a letter dated 25 February 1997 in which it gave details of MHB and suggested that Mr. Coates contact that firm.
58.	Prior to devising a scheme of remedial works for House 10 instructions were given to Brown to undertake soil investigations on Plot 10. Brown dug a trial pit on 10 December 1996 which was extended by a borehole from the bottom of the pit, and sank a second borehole. The trial pit was dug at the rear left-hand corner of House 10, viewed from the road, that being the location in which the most significant cracking seemed to have occurred. The other borehole was sunk in the front garden, to the right-hand side as viewed from the road. Logs of those investigations were put in evidence. The trial pit was taken to a depth of 2.5 metres, just below the foundation level, and the log recorded various roots of live and dead appearance down to that level. In the log of the borehole from the bottom of the trial pit hair and fibrous roots were recorded down to a depth of 2.9 metres. That borehole was taken to a depth of 5 metres and was recorded as dry on completion. The second borehole log recorded occasional hair and fibrous roots only down to 0.9 metres, although it too was taken to a depth of 5 metres. At that depth it was recorded as dry. A sample of root recovered from between 1.5 metres and 2.3 metres depth in the trial pit was sent to Richardsons for identification. In a letter dated 24 December 1996 to Brown Richardsons reported that the root was oak and had been alive shortly before being dug up.
59.	In the event the remedial scheme decided upon in the case of House 10 was also a piled raft underpinning. Invitations to contractors to tender for the necessary works were despatched, it seems from the terms of one of the tenders returned – that of Force Foundations Ltd., on or about 4 April 1997. Subsequently, in a letter dated 17 April 1997, Mr. Coates wrote again to the Council. The letter included:-
“We are instructed to deal with a subsidence claim at the above property and confirm site investigations have now been completed.
The site investigations have revealed a significant desiccation of the clay sub-soil and notable root encroachment has been identified from mature Oak trees located in woodland to the rear of our Principals Insured’s property. We understand that you are responsible for these trees and in the circumstances we should advise we will now be holding you liable in nuisance for encroachment of tree roots and seeking recovery of our Principals outlays.
The damage to our Principal’s Insured’s property is significant and at present we are currently awaiting receipt of tenders in respect of underpinning works required to be carried out.
In the circumstances, we would suggest that you pass a copy of this letter to your liability Insurers and await contact from appointed loss adjusters in due course.”
Expert evidence - general
60.	The case of Mr. and Mrs. Siddiqui in the Siddiqui Action and the case of Mr. Sohanpal in the Sohanpal Action depended, essentially, upon expert evidence to support the conclusion that the cause of the damage in respect of which a claim was made in each case was subsidence resulting from the abstraction of moisture from the soil beneath House 9, Garage 9 and House 10 by roots from oak trees in the Wood. In each case there was evidence from a structural engineer and from an arboriculturalist on behalf of the Claimants. The experts in each case were the same. The structural engineer was Mr. Andrew Marcham and the arboriculturalist was Mr. Christopher Davies. It was their evidence, really particularly that of Mr. Marcham, that the cause of the damage in each case was subsidence, and it was their evidence, really particularly that of Mr. Davies, that the cause of the subsidence was water abstraction by roots from trees in the Wood. Those conclusions depended upon the interpretation which they respectively placed upon the soil investigations to which I have already referred in the light of their expert knowledge and experience, and one or two other factors to which I shall refer.
61.	The expert evidence called on behalf of the Council in each case was also that of a structural engineer and that of an arboriculturalist. Again in each case the same individuals were involved. Mr. Andrew Billingham was the structural engineer and Dr. Frank Hope was the arboriculturalist. A consideration of substantially the same material as led Mr. Marcham and Mr. Davies to their conclusions that the cause of the damage in each case was subsidence resulting from water abstraction from the soil by roots of trees in the Wood led Mr. Billingham and Dr. Hope to the conclusions that the cause of the damage to House 9 and House 10 was heave caused by re-hydration of the soil beneath each which was desiccated at the time of construction as a result of the removal of trees formerly on the sites of Plot 9 and Plot 10 and the action up to that point of roots from trees in the Wood which would have been severed by the construction of the foundations of House 9 and House 10. In the case of Garage 9 it was accepted that the cause of damage was subsidence, but the likely cause was the action of vegetation in the garden of Plot 9 adjacent to Garage 9.
62.	Both Mr. Marcham and Mr. Billingham were first involved with Plot 9 and Plot 10 after the completion of the remedial work which forms the principal subject matter of the claim in each case. Each was therefore entirely dependent upon his interpretation of the records of damage and investigations made by others in reaching his conclusions. Indeed the report of each of Mr. Marcham and Mr. Billingham in each of the actions was very largely a recital of, and a commentary upon, such records.
63.	Dr. Hope was in the same position as Mr. Marcham and Mr. Billingham in not having been involved in either case until after the litigation had been commenced. Mr. Davies, on the other hand, had actually been instructed in relation to Plot 9 in 1998 and had prepared a report dated 6 February 1999 which was put in evidence.
Expert evidence – the Siddiqui Action
64.	In considering the expert evidence in the Siddiqui Action it is convenient to begin with that of the arboriculturalists. Mr. Davies and Dr. Hope plainly put much effort into a consideration of what they could agree, to great benefit, and recorded what they did agree in a document which was put before me. That document included the following:-
“5. It is agreed that the shrubs to the left-hand side of the garage, identified as plant 4 in the plan produced by FH, consists of a Climbing Hydrangea, a Honeysuckle, and an Elaeagnus shrub. The plants were located at 0.5 metres range from the garage.
6. It is agreed that the Lawson’s Cypress conifer also included in the group identified as plant 4 in the plant [sic] produced by FH was located 2.0 metres away from the rear, of the garage….
20. It is agreed that if the soil was dry and too stiff to excavate below a depth of 1.3 metres, this indicates that the soil had almost certainly been dried by vegetation...
22. It is agreed that the soil beneath the garage was desiccated, according to the simplistic Driscoll formula (0.4 x Liquid limit).
23. It is agreed that using the simplistic Driscoll formula there was not significant desiccation beneath the house (based on figures produced by Eastern Soil Search Ltd., dated the 8th of June, 1998, RM Brown’s reports, dated the 27th of August, 1991 and March 1992, and the Sinclair Jonson [sic] report dated the 14th of November, 1991…
27. It is agreed that water was present beneath the foundations of the house according to the borehole logs (RM Brown report, February, 1998). Internal seepage was present in borehole number 2, at a depth of 3.4 metres below ground level, and in borehole number 3 (front of the house), seepage was present at a depth of 4.7 metres…
30. It is agreed that the maximum depth from which roots were removed  from beneath the garage was 3.6 metres, and that the maximum depth of roots found beneath the house was 3.2 metres.
31. It is agreed that Oak roots were identified beneath the foundations of the garage, and that the only likely source of these roots was the trees growing in the woodland to the rear of the property.
32. It is agreed that no roots from beneath the house had been formally identified…
34. It is agreed that the R.M. Brown report, produced on the 11th of October, 1991, indicated that no roots were found in trial pit/borehole number 1 below a depth of 2.3 metres.
35. It is agreed that all roots to a depth of 3.9 metres would have been severed during the underpinning operation to the rear of the house. It is further agreed that the severed roots would no longer function, and thus extract moisture from beneath the house. [This refers, as was made clear in oral evidence, to that part of the root which had been cut off from a tree, not to that part which remained attached to a tree.]..
37. It is agreed that there is no current evidence of Oak roots beneath the 3.9 metre underpinning.
38. It is agreed that according to the Simmons report on aerial photography, taken in 1969, tree 39 (a 1.8 metre high tree – species unknown) would have been within the area now occupied by the footprint of number 9 Laburnum Grove.
39. It is agreed that the house was built approximately 11 years after the photograph was taken, and that if the tree remained on site, it is likely to have continued to grow. As such it would have affected the moisture content…
46. It is agreed that the Oaks would not be likely to remove significant amounts of moisture from the soil before the end of May.
47. It is agreed that the shrubs and conifer located to the rear of the garage would have been adversely affecting the soil moisture beneath the foundations of the garage.
48. It is agreed that it is not possible to identify which vegetation has actually caused the damage to the garage. It is further agreed that it is not possible to assess what proportion any one tree is contributing to the damage to the garage….”
65.	The effect of Mr. Davies’s evidence on matters not agreed in the Siddiqui Action can be summarised quite simply. It is notorious that oak trees are a major cause of subsidence. The area of influence, that is to say, the radius within which the roots may be expected to affect the moisture content of the soil, of oak trees can be up to 35 metres. House 9 and Garage 9 are within 35 metres of where there were, until they were cut down, oak trees in the Wood. Therefore the cause of any subsidence of the soil beneath House 9 or Garage 9 was oak trees in the Wood. In his report in the Siddiqui Action at paragraph 1.1.3 Mr. Davies put his view in this way:-
“1998 site investigations were undertaken. Roots that have been identified as emanating from Oak were recovered during geotechnical site investigations from beneath foundations in trial pit/borehole to the rear right corner of the garage. These roots were noted at depths of up to 3.6 metres. Roots were also recovered from a trial pit within the property footprint to a depth of 3.2 metres but these were not identified. I consider that these roots are most likely to have emanated from Oak trees to the rear of the property as these are the closest and this species is capable of rooting to depths greater than the 3.2 metres at which they were recovered. According to Cutler & Richardson (1989) Oak is the most common species to be implicated in subsidence damage and accounts for 11.5% of all known cases at the time. I have personal experience of Oak roots having been recovered from depths of over 5 metres.”
As became clear at trial, what this view involved so far as House 9 was concerned was the proposition that roots from oak trees in the Wood, which at the time of the initial underpinning of the rear of House 9 were not noted at any depth below 3.2 metres, burrowed down to at least 3.9 metres to get under the underpinning then ascended towards the surface in order to be found at a depth of 3.2 metres below the dining room of House 9 or that they operated a pincer movement upon the underpinning, entering the soil below the un-underpinned foundations forward of the extent of underpinning. It also involved the notion that oak trees which Mr. Davies himself estimated at between 100 and 120 years old, and on the threshold, at least, of maturity, would continue to extend their root systems and overcome substantial physical barriers to do so.
66.	In his first report for the purposes of the Siddiqui Action Dr. Hope included an illuminating section concerning the significance of the finding of decayed wood in ground investigations on Plot 9. It is worth quoting the section substantially in full.
“15.1 The R. M. Brown Foundation Investigation Ltd., soil log data for trial pit 1, in the front lounge of the house shows that occasional old, decomposing roots of up to 2mm diameter were present to a depth of approximately 4.0 metres below ground level.
15.2 The NHBC borehole log for trial pit number 1 (dated the 19/11/987 [sic]), i.e. at the rear right-hand corner of the house, show that odd pieces of decayed wood were present between 3.0 metres and 3.5 metres below ground level.
15.3 The presence of the old decaying wood and roots is highly significant, as it must either have been introduced within fill material/Made Ground, or it must have emanated from trees which were previously growing on site. As the depth of the dead wood and roots is between 3.0 and 4.0 metres, it is improbable that it was introduced in any fill, or Made Ground. It is also highly improbable that it emanated from the trees in the woodland. 
15.4 The most probable and logical explanation as to why the dead wood and roots were present beneath the house, is that they were left in situ when the previous trees were removed, i. e. prior to the house being constructed.
15.5 There is a commonly held misconception that trees have roots that are produced predominantly downwards, and that anchoring roots are very thick and descend into the soil for many metres. What actually happens is that the majority of tree roots grow more or less parallel to the soil surface, and are relatively shallow (within the top 1.0 metre). They can radiate out for considerable distances, often to the mature height of the tree, and can be 30cm or more wide at the base of the trunk. They sub-divide and taper rapidly away from the trunk, and are often only 2cm to 3cm in diameter at a distance of 3-4 metres away from the trunk (Ref: “Driveways Close To Trees”, Dobson & Patch, AAIS Practice Note 1, 1996).
15.6 If the picture on the following page, of the accurate representation of a tree’s root system, is studied, it will be clear that the greatest depth of roots will be directly beneath the trunk of the tree, and that the remainder of the root system will be close to ground level.
15.7 Oak is a species which can produce deep roots, although they typically follow the general growth pattern, by having the deepest roots close to the trunk. The mass of roots close to the base of the trunk is commonly known as the “Root Plate”.
15.8 Research has been carried out to verify the extent of tree root plates. The majority of the work was compiled after the great storm of 1987, where many thousands of trees were blown over, exposing their root plates. The definitive publication on the subject is entitled “Tree Root Plate Morphology”, by D.F. Cutler, P. E. Gasson & M. C. Farmer. It was first published by the Arboricultural Association, and later by A. B. Academic Publishers in 1990….
  15.10 The data relating to Oak show that the majority of roots within the root plate grow down to a depth of between 1.0 metre and 2.0 metres below ground level, although a few roots have been found to extend beneath 2.0 metres.
15.11 The data also show that the majority of tree root plates of Oak extend for between 1.0 metre and 5.0 metres, with a few large trees extending more than 5.0 metres. The above data suggest that the claim made by Mr. Davies, i. e. that significant numbers of live roots could be present beneath a depth of the 3.9 metre underpinning, at a distance of over 10.0 metres from the trees is untenable.
15.12 The depth of the roots and decaying wood beneath number 9 Laburnum Grove is between 3.0 and 4.0 metres, and the trees are all over 10.0 metres away from the rear wall of the house. The data clearly highlight the fact that there is an extremely low probability that the dead wood and roots emanated from the Oaks in the Woodland. They must have originated from trees which were on site prior to the house being built.
15.13 Old decaying wood and roots beneath a building will have a profound influence on the characteristics of the soil. The presence of such materials can indicate that there would have been a significant, and almost certainly persistent moisture deficit, in the soil prior to the removal of the trees, which would inevitably lead to upward movement of the soil as it re-hydrates during the decaying process. Alternatively, it could indicate that excessive settlement over a long period of time could occur. The settlement need not be uniform, and could manifest itself in localised areas where the largest amount of decaying woody matter is present. If such settlement did occur, it could, at first blush appear to be subsidence.”
The research data to which Dr. Hope referred was not disputed at trial. I found Dr. Hope to be an impressive witness, with a sounder scientific grounding than Mr. Davies, whose evidence seemed substantially to be based really on his personal experience. Mr. Davies seemed to me to have no answer to Dr. Hope’s analysis in section 15 of his report. I accept that analysis and reject what seems to me anyway as a matter of common sense the wildly improbable hypothesis advanced on behalf of Mr. and Mrs. Siddiqui of how roots from oak trees in the Wood could have overcome the obstacle which the underpinned rear foundations presented to forward movement of their roots, even if, as to which I have considerable doubts in the light of the maturity of the relevant trees, they had wished to move forward into the area of the footprint of House 9. 
67.	Another section of Dr. Hope’s first report in the Siddiqui Action which I have found of considerable assistance was section 17, in which he considered specifically the issue whether roots of trees in the Wood would have affected the moisture content of the soil beneath the footprint of House 9 after the underpinning of the rear foundations. I accept what he wrote in that section, which was:-
“17.1 The data in the Publication entitled “Tree Root Plate Morphology” clearly show the natural extent and depth of the root plate of Oaks, and the figures highlight the fact that the majority of the feeding roots would be within the top 2.0 metres, of the soil surface. Roots would develop deeper than 2.0 metres, but their percentage of the total root mass would be extremely small.
17.2 As the underpinning of the house was down to a depth of 3.9 metres all of the tree roots would have been completely severed to that depth during the under-pinning work…
17.3 The growth of tree roots is effectively controlled by the bulk density of the soil and its oxygen content. Once the oxygen content drops below between 10% and 15% root growth decreases significantly, whilst when it drops to 5% root growth almost ceases. The majority of available oxygen is found close to ground level, and that is why the majority of roots of trees are found within the top 1.0 metre or so of the soil surface.
17.4 It is very unlikely that the roots of the woodland trees would have re-generated at a depth of over 3.9 metres, and I consider it unrealistic to claim that the damage to the front of the house after underpinning took place was due to the roots from the trees in the woodland. The trees were simply too far away, and the underpinning was too deep to allow this to happen.
17.5 The moisture removal from the front of the building, especially at the front, right-hand corner would almost certainly have occurred due to the shrubs and conifer growing right-up against the corner of the building … Unfortunately, no investigations were carried out in this area, and so the presence of the conifer and shrub roots was not confirmed.”
68.	While, at some points in his evidence, Dr. Hope envisaged the possibility that the cause of the damage to House 9 was subsidence, I am satisfied that that is not so. The evidence of Dr. Hope concerning the actions and activities of the roots of oak trees is one of the factors which has led me to my conclusion, because if, as I do, I accept the evidence of Dr. Hope that the roots of trees from the Wood could not have caused moisture to be abstracted from the soil under the footprint of House 9 at the time of the damage in 1997, what other cause of moisture abstraction could there be which could have caused that damage? In my judgment the answer is none. It seems to me that at the time of construction of House 9 conditions were ripe on Plot 9 for the occurrence of heave. Tree 39 was not, perhaps, particularly large, but it was right on the footprint of House 9 and, on my findings, was removed only shortly before House 9 was built. Until removal Tree 39 must have drawn moisture from the soil on which it stood and there created at least a local moisture deficiency to whatever depth its roots went and however widely they spread. Until House 9 was built there was no obstacle to the spread of roots from trees in the Wood, in particular the large trees Tree 41, Tree 42 and Tree 43, into the area which became Plot 9. On the evidence of Dr. Hope, which I accept, the roots which so spread are likely to have spread at a depth of between 1 and 2 metres below ground level. There was no reason for them to go any deeper. However, at between 1 and 2 metres depth they would have been abstracting moisture at a depth which would not have been re-hydrated by seasonal rainfall, so there would have been desiccation. The roots, on the evidence of the ground investigations to which I have referred, may have gone as deep as 3.2 metres below ground level. I accept the evidence of Dr. Hope that the discovery of dead roots beneath, and decaying wood adjacent to, House 9 indicate that there had formerly been vegetation on the footprint of House 9, the removal of which would have been conducive to heave. The ground investigations to which I have referred did not at any stage reveal clear evidence of desiccation, which would be necessary if the mechanism of damage was to be subsidence, after House 9 was built. The results of Mr. Chamberlain’s digging of his Trial Pit 2, however, provide clear evidence that ground in the vicinity was desiccated at a depth of 1.3 metres in December 1979, which was outside the growing season and at a time of year when re-hydration would usually be expected to be taking place. Such desiccation would be a necessary precondition to heave. As I have pointed out, the slight evidence of desiccation found in the 1988 investigation of the soil at Plot 9 is logically consistent with a soil which has been desiccated and is re-hydrating not yet having achieved equilibrium. On the other hand, there was fairly clear evidence of moisture at depth in some soil investigations which ruled out subsidence at the points sampled, but was consistent with heave. There was also evidence, which I shall explain in more detail a little later, that a comparison of the levels of House 9 as surveyed by Gallie and by Gryphon showed that, with the exception of the rear right-hand corner, the level of House 9 had risen between the Gallie survey and the Gryphon survey. I accept that evidence. Looking at the totality of the evidence, in the light of the expert evidence as to the indicia of heave and of subsidence, respectively, I am satisfied that what House 9 suffered from in 1997 was heave. If necessary, I should have found that that was the cause of all the problems going right back to 1988. It would certainly have explained both why the partial underpinning solution adopted in 1988 was unsuccessful and why Mr. Siddiqui noticed the recurrence of damage within weeks of the completion of the underpinning works.
69.	Mr. Marcham’s opinion that the cause of the damage to House 9 was subsidence was, as was clear from his report dated 26 February 2003 in the Siddiqui Action, the result of a process of elimination. He was satisfied that the cause was not heave, therefore it had to be subsidence. An illustration of his approach was what he said about the damage to House 9 with particular reference to that in 1987, which he called “Phase 1 damage”, in paragraph 8.6 of his report:-
“It is evident from the Simmonds [sic] aerial survey and also from the witness statement of Mr. George Mist, that there were no trees of any significance located beneath or in close proximity to the house on Plot 9, Laburnum Grove at or before time of construction. The main ingredient required for a heave damage scenario therefore appears invalid from the outset with particular regard to Phase 1 damage.”
For the reasons which I have given I do not interpret the evidence available to me in the same way he does. When differing interpretations were put to him in cross-examination and he was asked to consider the significance of particular points he showed himself, in my judgment, to be rigid and inflexible. Rather than adopting an independent position, as befits an expert witness called to assist the Court, he argued with Counsel cross-examining him. It was plain to me that, unusually in these days, he saw his role more as an advocate for his clients rather than a dispassionate provider of technical help to me. I did not find his evidence at all helpful. While Mr. Billingham seemed convinced of his conclusions, and more than once slipped into describing his opinion as “my case”, not only in my judgment did he have good grounds for his conclusions, such that he was entitled to be convinced as to their correctness, but he also showed himself much more balanced and open-minded in considering in cross-examination other possibilities. A telling piece of evidence given by Mr. Billingham, which I accept as accurate, and to which I have already referred, was that a comparison of the levels plotted by Gallie and by Gryphon showed that House 9 had, except at the rear right hand corner, risen between the dates of the two surveys. If that was so, it could only be consistent with heave being the mechanism of damage. Mr. Marcham accepted the logic of that, but contended that the levels recorded in the Gryphon survey showed that there must be errors. I do not accept that. What the nature and effect of the alleged errors were was not clearly explained. It was suggested that, for the comparison of levels undertaken by Mr. Billingham to be correct, the underpinned foundation must have risen also. So be it.
70.	As I have already recorded, it proved to be common ground that the cause of damage to Garage 9 in 1997 was subsidence. That was not suggested to be inconsistent on technical grounds with the contention that the cause of the damage to House 9 was heave, and was not inconsistent, in my judgment. There was no reason why different parts of Plot 9 should not be subject to countervailing movements of the soil at the same time. The question then is what was the cause of the subsidence in the soil under Garage 9? In the light of the matters agreed between Mr. Davies and Dr. Hope, which I accept on this point, one cannot say. Dr. Hope was pressed in cross-examination on the issue and he said his prime candidate for causing the damage would be the Lawson’s Cypress tree 2 metres away from the corner of Garage 9 which had suffered damage. If compelled to make a finding, I should accept that evidence of Dr. Hope, by whose evidence, as I have said, I was very impressed. However, it is enough for present purposes that I should accept what Dr. Hope and Mr. Davies agreed about it for the claim in relation to Garage 9 to fail for want of proof. 
Expert evidence – the Sohanpal Action
71.	At paragraph 8.2 of his report in the Siddiqui Action Mr. Marcham gave evidence, which was not contested, that periods of severe drought since the Second World War have been 1947, 1975 – 1976, 1989 – 1992 and 1995. On the evidence in the Sohanpal Action House 10 sustained no damage as a result of the extended period of severe drought between 1989 and 1992, which fact was urged upon me by Mr. Lord, convincingly as it seemed to me, as an indication that whatever was the cause of the damage to House 10 in 1995 it was not subsidence. The point was reinforced, submitted Mr. Lord, by the fact that, according to Mr. Sohanpal’s insurance claim form, which I have already indicated I accept as accurate in this regard, damage to House 10 first occurred during the winter, which is not the growing season for deciduous trees in Southern England.
72.	Mr. Lord relied heavily, in support of the Council’s case that the cause of the damage to House 10 in 1995 was heave, upon the presence, location, number and size of the trees present upon the site of what became Plot 10 before the construction of House 10, specifically Tree 38, right on the right hand rear corner where the worst damage to House 10 occurred, Tree 36 just outside the footprint of House 10 on the rear left corner, Tree 37 in the rear garden, and Trees 34 and 35 in the front garden. Not to be overlooked, submitted Mr. Lord, was Tree 23 in the curtilage of the Public House, which was still there. All of these were very telling points. While it was correct that Garage 10, immediately beneath Tree 23 had not suffered damage, Mr. Lord submitted that that was probably because the foundations of that building would have been relatively shallow. That may be, but there was in fact no evidence as to the depth of the foundations of Garage 10.
73.	Mr. Davies and Dr. Hope reached agreement as to a number of matters for the purposes of the Sohanpal Action and set those matters out in a document which was put before me. What was agreed included:-
“3. It is agreed that prior to construction of the house, trees were present within, or directly adjacent to the footprint of the house. It is agreed that three further trees, previously removed, were within the grounds of the property. It is agreed that all of these trees would have been capable of affecting the soil moisture within the curtilage of the property.
4. It is agreed that trees 23, 40 and 41 on the Simmons plan were large prior to construction of the house, and that all of these trees would have been capable of affecting the soil moisture within the curtilage of the property…
6. It is agreed that the large Oak (number 1 on the plan produced by FH on the 12th of April, 2002 [i.e. Tree 23]), would be likely to have the greatest influence on soil moisture beneath the house, due to its proximity and size…
8. It is agreed that we cannot, therefore, identify which specific trees were the substantial cause of the damage to the house…
15. It is agreed that the roots from trial pit/borehole 1, from between 1.5 and 2.3 metres deep, were formally identified as Oak, and that they probably emanated from the trees in the woodland to the rear. 
16. It is agreed that roots in borehole 2, if shown to be Oak, would probably have originated from the Oak (plant 1 on the plan produced by FH), i.e. the Oak within the grounds of the public house.
17. It is agreed, based on the above, that the currently available site investigations are inadequate to provide an accurate assessment of the soils, roots and damage to the building.
18. It is agreed that the mere presence of roots beneath foundations does not necessarily indicate that the trees are the cause of damage…
22. It is agreed that the limited data indicates that any tree related involvement appears greater to the front of the house than to the rear.
23. It is agreed, based upon the above, it appears the Local Authority trees to the rear are unlikely to be the main causal factor in the current damage. 
24. It is agreed that the data indicate that tree 1 (as identified in the plan produced by FH), growing in the grounds of the public house, would be likely to be the substantial cause of any tree-related damage…
28. It is agreed that if the damage to the house is found to be caused by heave, the soil would have been desiccated prior to construction by the pre-existing trees and by trees currently growing near-by.
29. However, it is agreed that should the damage be found to be caused by subsidence, the most likely cause would be the closest Oak tree (tree 1 on the FH plan) within the car park of the Plough public house. The lesser contribution of other trees cannot be ruled out.”
74.	Mr. Davies sought, shortly before the start of the trial, to go back upon what he had agreed with Dr. Hope as set out in the preceding paragraph. Unhappily that effort did him no credit. He sought to say that at the time he made his agreements with Dr. Hope he was under a misapprehension as to where the principal damage in House 10 had been. That was demonstrated to be untrue by a reference in his report in relation to the Sohanpal Action at paragraph A to having been provided prior to his meeting with Dr. Hope with a copy of a report of Mr. Marcham dated 9 November 2001. Consideration of that report showed that the description of the damage to House 10 given was consistent with the evidence as to the location of the principal damage given to me. Mr. Davies did not provide a convincing explanation as to how, in those circumstances, he came to make his alleged mistake, and I am satisfied that he did not make a mistake. To put it colloquially, once it was appreciated that the effect of the matters which he had agreed with Dr. Hope made the claim in the Sohanpal Action all but unsustainable, he was “nobbled” to change his evidence. I am satisfied that the agreements which he originally made were proper agreements for him to have made and that they do have the feared consequence of dooming the claim in the Sohanpal Action. Mr. Davies’s attempt to identify the Council’s trees as responsible for the damage to House 10 in his report dated 26 February 2003 prepared for the purposes of the Sohanpal Action on its face lacked all conviction, as it seemed to me. The relevant passages were:-
“2.1.2 There are three Oak trees within 18 metres of the property. Oak T5 was located within the council woodland to the rear and is the closest tree to the area of damage to the rear left hand corner at approximately 9 metres, well within its species’ common influencing distance.
One further Oak within the council woodland was approximately 14 metres from the closest part of the building, the rear right hand corner. 
The closest Oak tree to the building (T1) is within land attached to The Plough public house. The tree was 7.6 metres from the right hand front corner of the property but approximately 15 metres from the main area of damage at the rear left hand corner)….
3. Based on the available evidence and reports by engineers, I am of opinion that the substantive and effective cause of damage to the rear of the property was Oak T5, owned by the council, with a lesser effect by Oak T3. The damage to the rear right hand side of the property and the front right hand corner is likely to have been caused by the combined effects of Oak T5 and Oak T1.”
I reject those passages as genuinely setting out Mr. Davies’s views and as accurate.
75.	In his first report prepared for the purposes of the Sohanpal Action Dr. Hope said in paragraph 18.5, in a passage which I accept as accurate:-
“Number 10 Laburnum Grove was built on the site of a previous orchard containing large trees, but no investigations appear to have been carried out to ascertain the moisture status of the soil prior to the house being built. There is a very high probability that the trees in the orchard would have produced a significant moisture deficit beneath their root plates, and once they were removed, the soil would gradually re-hydrate. Any such re-hydration of a significant moisture deficit would inevitably lead to swelling of the soil, i.e. heave.”
76.	Mr. Marcham expressed the view in paragraph 7.1 of his report prepared for the purposes of the Sohanpal Action that:- 
“damage sustained to the property has been occasioned solely by root desiccation shrinkage in the underlying clay subsoil conditions due to the uncontrolled growth of Oak trees present beyond the rear boundary in Ruislip Wood.”
In cross-examination it became apparent that the principal justification for the conclusion that the cause of the damage was subsidence which Mr. Marcham put forward was that the pattern of crack damage on the rear of House 10 was in his view indicative of subsidence, not heave. Mr. Billingham expressed the view that, to the contrary, the pattern of crack damage seemed to him to be classic evidence of heave. Mr. Marcham did not go into much detail as to the justification for his view. In the end the quality of his analysis was along the lines, “I have seen many elephants in my time. I know an elephant when I see one. This is an elephant.” Mr. Billingham at least favoured me with the explanation in support of his view that the cracks reported in the rear elevation of House 10 were wider at the bottom than at the top. Mr. Marcham contested whether that was so, which seemed an implicit recognition that if it was so, it indicated what Mr. Billingham said it indicated. I am satisfied on the photographic evidence put before me, especially of the area of cracking around a patio door, that the cracking was wider at the bottom, or lower, level, and tapered to nothing at the top. I accept the evidence of Mr. Billingham as to what that signifies.
77.	The other particular point upon which Mr. Billingham relied in support of his view that the cause of damage to House 10 was heave was what he contended was clear evidence that the front porch slab at House 10 had risen. Mr. Marcham, with the greatest reluctance, as it seemed to me, at length accepted that the evidence did indeed indicate that the front porch slab at House 10 had risen as a result of heave. However, he then sought to persuade me that that circumstance told one nothing about the cause of the damage to the main part of House 10. He told me that the foundations of the porch might be very shallow, which seemed to be pure speculation on his part. What he would have me believe, as it appeared to me, was that the soil might be subject to heave on the outside of the front door, as it were, whilst being subject to subsidence on the inside of the front door. Whilst I recognise that different parts of a plot of land may contemporaneously be subject to subsidence and heave, it does not seem particularly likely that these different effects should be observed dramatically within a distance of a couple of feet. In the end I concluded that Mr. Marcham was simply trying to marginalise a piece of evidence which was inconvenient to the position which he had adopted.
78.	I reject the evidence of Mr. Marcham also in relation to the cause of the damage to House 10. I find that the cause of the damage sustained in 1995 was heave. Consequently the claim in the Sohanpal Action also fails.
The Law
79.	In the light of my conclusions as to the nature and cause of the damage in each of the Siddiqui Action and the Sohanpal Action, it is not strictly necessary to consider the other lines of defence advanced on behalf of the Council. However, as I have heard all of the relevant evidence and argument, it is convenient that I should indicate my conclusions on those issues.
80.	It was, I think, common ground that the approach which I should adopt to the questions of reasonable foreseeability and abatement was that indicated by the House of Lords in Delaware Mansions Ltd. v. Westminster City Council [2002] 1 AC 321. The only substantive speech in that case was that of Lord Cooke of Thorndon. At pages 332 to 334 of the report Lord Cooke said this, so far as is presently material:-
“29. Beyond that I think that the answer to the issue falls to be found by applying the concepts of reasonableness between neighbours (real or figurative) and reasonable foreseeability which underlie much modern tort law and, more particularly, the law of nuisance. The great cases in nuisance decided in our time have these concepts at their heart. In Sedleigh-Denfield v. O’Callaghan [1940] AC 880, the House of Lords held that an occupier of land “continues” a nuisance if, with knowledge or presumed knowledge of its existence (in that case a defective grating giving rise to flood damage), he fails to take reasonable means to bring it to an end when he has reasonable time to do so. In Overseas Tankship (UK) Ltd. v. Miller Steamship Co Pty [1967] 1 AC 617, the second Wagon Mound case, the Privy Council, approaching the case under the rubrics of both nuisance and negligence, said, at p 644 per Lord Reid: “If it is clear that the reasonable man would have realised or foreseen and prevented the risk, then it must follow that the appellant is liable in damages.”…
31. In both the second Wagon Mound case and Goldman v. Hargrave the judgments, which repay full rereading, are directed to what a reasonable person in the shoes of the defendant would have done. The label nuisance or negligence is treated as of no real significance. In this field, I think, the concern of the common law lies in working out the fair and just content and incidents of a neighbour’s duty rather than affixing a label and inferring the extent of the duty from it….
33. Approaching the present case in the light of those governing concepts and the judge’s findings, I think that there was a continuing nuisance during Flecksun’s ownership until at least the completion of the underpinning and piling in July 1992. It matters not that further cracking of the superstructure may not have occurred after March 1990. The encroachment of the roots was causing continuing damage to the land by dehydrating the soil and inhibiting rehydration. Damage consisting of impairment of the load-bearing qualities of residential land is, in my view, itself a nuisance. This is consistent with the opinions of Talbot J in the Masters case [1978] QB 841 and the Court of Appeal in the instant case, although neither Talbot J nor Pill LJ analysed specifically what they regarded as a continuing nuisance. Cracking in the building was consequential. Having regard to the proximity of the plane tree to Delaware Mansions, a real risk of damage to the land and the foundations was foreseeable on the part of Westminster, as in effect the judge found. It is arguable that the cost of repairs to the cracking could have been recovered as soon as it became manifest. The point need not be decided, although I am disposed to think that a reasonable landowner would notify the controlling local authority or neighbour as soon as tree root damage was suspected. It is agreed that if the plane tree had been removed, the need to underpin would have been avoided and the total cost of repair to the building would have been only £14,000. On the other hand the judge has found that, once the council declined to remove the tree, the underpinning and piling costs were reasonably incurred, despite the council’s trench.
34. It is at this point that I see Solloway v. Hampshire County Council 79 LGR 449 as important as a salutary warning against imposing unreasonable and unacceptable burdens on local authorities or other tree owners. If reasonableness between neighbours is the key to the solution of problems in this field, it cannot be right to visit the authority or owner responsible for a tree with a large bill for underpinning without giving them notice of the damage and the opportunity of avoiding further damage by removal of the tree. Should they elect to preserve the tree for environmental reasons, they may fairly be expected to bear the cost of underpinning or other reasonably necessary remedial works; and the party on whom the cost has fallen may recover it, even though there may be elements of hitherto unsatisfied pre-proprietorship damage or protection for the future. But, as a general proposition, I think that the defendant is entitled to notice and a reasonable opportunity of abatement before liability for remedial expenditure can arise. In this case Westminster had ample notice and time before the underpinning and piling, and is in my opinion liable.”
81.	The question what was involved in giving a tree owner a reasonable opportunity to abate a nuisance caused by tree roots was considered by the Court of Appeal in L. E. Jones (Insurance Brokers) Ltd. v. Portsmouth City Council [2002] EWCA Civ 1723. The only substantive judgment was that of Dyson LJ. At paragraph 22 of his judgment he said:-
“…What is a reasonable opportunity to abate the nuisance is a question of fact. The judge made a clear finding on this issue. This court should be very slow to interfere with such a finding. Portsmouth did not respond to the letter of 2nd September. It did not ask the insurers for time to investigate the cause of the damage, or to explore other measures than underpinning. In particular it did not ask for time to consider whether the problem could or should be solved by removal or severe reduction in the height of the offending trees. In any event, Portsmouth did not satisfy the judge that, if it had been given more time, it would have abated the nuisance by tree management. In this respect, it is significant that Portsmouth contested the issue of causation right up to the trial, and at no time following receipt of the letter of 2nd September, did it say that it would resolve the problem by removing or reducing the height of the trees.”
Reasonable foreseeability – the Siddiqui Action
82.	In the Siddiqui Action Mr. Lord submitted, first, that bearing in mind the date of the construction of House 9 and the fact that it was constructed apparently in compliance with the guidelines as to foundation construction of NHBC, the Council had no reason reasonably to foresee the risk of any damage to the structure of House 9 from the roots of trees in the Wood until such damage in fact occurred, assuming, contrary to my findings, that such was the occasion of damage to House 9. I accept that submission. Modern standards of construction can be expected to take account of obvious hazards in the vicinity of the structure to be built, as the trees in the Wood were in relation to any structure to be constructed on Plot 9.
83.	Then Mr. Lord submitted that, after the first occurrence of damage to House 9, the Council had no reason reasonably to foresee the risk of a recurrence of damage, bearing in mind that the objective of the underpinning works undertaken at that time was to eliminate such risk. That submission seems to conflate two separate issues. The first of those issues is what was it, after the first occurrence of damage, that the Council knew about what had happened. The second is what assumptions, in the light of that knowledge, the Council was entitled to make about the risks for the future. The effect of the decision of the House of Lords in Delaware Mansions Ltd. v. Westminster City Council, so far as is presently material, it seems to me, is that the Council should be taken to have foreseen what it did actually foresee, or what it ought to have foreseen as a reasonable landowner. There was no evidence before me of any actual consideration on the part of the Council of any risk of damage to House 9. The only material from which I can draw any inferences is the evidence as to what the Council did, or caused to be done, in relation to the trees in the Wood in 1992 and 1998. However, it is plain that the Council was put on notice by Mr. Breed’s letter of 1 August 1988 of the occurrence of damage to House 9, and the receipt of such notice should have put the Council, as a reasonable landowner, on notice of the risk of further damage to House 9 unless some appropriate steps were taken. The same letter indicated that remedial works were intended, but not what. It seems to me that the Council was not entitled to make any assumptions as to the likely or intended effect of such works in relation to the risk which had by then, on the hypothesis which must be adopted in relation to my consideration of the issues in this part of this judgment, eventuated. The Council, in my judgment, is not entitled to rely upon what it would have discovered if it had enquired as to the nature of the works undertaken in 1988 as negativing foreseeability as it made no enquiries at the time and placed no reliance upon what it might have learned, but did not.
84.	Quite apart from the point considered at the end of the preceding paragraph, by Mr. Breed’s letter dated 7 October 1991 the Council was again put on notice of the occurrence of damage to House 9. Whatever assumptions it might have been entitled to make up to that point about the risk of damage from trees in the Wood, from that time forward, on the hypothesis adopted, it was reasonably foreseeable that the trees could cause damage. The Council at that stage plainly recognised the risk and took steps to reduce or avoid it, namely by pruning trees in the Wood. However, it took no steps to put in place, or to maintain, any regime of continued management of trees which could affect House 9. No further work was done until 1998, after yet a further instance of damage. In all the circumstances, had it been necessary to do so, I should have held that damage to House 9 from trees in the Wood was reasonably foreseeable by the Council from the date of receipt of Mr. Breed’s letter dated 1 August 1988, or at the latest, from the date of receipt of his letter dated 7 October 1991.
Reasonable foreseeability – the Sohanpal Action
85.	 Mr. Lord submitted that the damage which occurred to House 10 in 1995 was not reasonably foreseeable because the Council was entitled to make the same initial assumption in relation to its standards of construction as in relation to House 9 and no damage had occurred until that complained of in the Sohanpal Action. If the circumstances in relation to House 10 were all that fell to be considered, I should have accepted the submission of Mr. Lord. However, in my judgment the question of whether damage to a structure is reasonably foreseeable falls to be determined not in a vacuum, but in the light of what a reasonable landowner knew or ought to know about adjacent properties and on the basis of which he ought to make his assessment of the risk to the structure in question. In other words, in the light of what, by 1995, the Council knew about the damage to House 9, it was reasonably foreseeable that there was a risk to House 10. Any assumption which it might have been reasonable to make about the adequacy of the foundations of House 10 was undermined by the occurrence of damage to House 9 which was constructed by the same builder at the same time as part of the same development. If the foundations of one house were inadequate to resist the action of tree roots, so might be the foundations of the house next door.
Abatement – the Siddiqui Action
86.	While Lord Cooke in Delaware Mansions Ltd. v. Westminster City Council considered the questions of giving notice of damage to a tree owner and an opportunity to him to abate the nuisance by removal of the tree which has caused the damage, it is wrong, in my judgment, to treat those matters as conditions precedent to recovery of damages in a case of damage caused by tree root incursion, such that, absent notice and the affording of an opportunity to remove, no recovery is possible. Although Lord Cooke did not himself articulate it, in my judgment it is implicit in his consideration of the points as to notice and opportunity to do works to the offending tree that in the circumstances of the particular case if the tree is removed the remedial works proposed will either be rendered unnecessary or can be less extensive. That was the situation in Delaware Mansions Ltd. v. Westminster City Council  itself. In a case in which it makes no difference to the required works nothing is achieved by giving notice and an opportunity to remove the guilty tree. Thus it is, it seems to me, for him who contends that the remedial works would either have been unnecessary or less extensive had the relevant tree been removed to demonstrate that by evidence. Unless he does so, the questions of whether notice of intended works and an opportunity to remove the offending tree have been given do not sensibly arise. In the Siddiqui Action there was no evidence that the works in fact undertaken in 1999 would have been unnecessary or less extensive if some tree or trees in the Wood had been removed. As some trees were removed and others reduced in 1998, yet still the works the cost of which was claimed were undertaken, the only sensible conclusion is that the removal of trees and reduction of trees had no impact upon the necessary works. Thus this line of defence would have failed, had it been necessary to rely upon it. In any event it seems to me that by his letter dated 12 January 1998 Mr. Breed gave ample notice and opportunity to the Council to seek to avoid the need for remedial works as extensive as were in fact undertaken by works to the trees in the Wood, if that was what the Council wanted to do.
Abatement – the Sohanpal Action
87.	 There was no evidence in this action either that the need for works as extensive as those in fact undertaken to House 10 could have been avoided by some works to the trees in the Wood. For that reason the defence based upon loss of any opportunity of abatement would have failed in this action also. Had it been necessary to do so, however, I should also have held that Mr. Coates’s letter dated 17 April 1997 did afford the Council an adequate opportunity to suggest the undertaking of works to the trees in the Wood as an alternative to the undertaking of works to House 10, had it wished to do so.
Conclusions
88.	For the reasons which I have given in relation to the Siddiqui Action the claims in that action fail and that action is dismissed.
89.	For the reasons which I have given in relation to the Sohanpal Action the claims in that action also fail and that action is also dismissed.