Case No: A3/2001/0760
Neutral Citation Number: [2002] EWCA Civ 465 
IN THE SUPREME COURT OF JUDICATURE
COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE PATENTS COUNTY COURT
PETER PRESCOTT QC (SITTING AS A DEPUTY JUDGE
OF THE PATENTS COUNTY COURT
Royal Courts of Justice
Strand, 
London, WC2A 2LL

Thursday 25th April 2002
Before :

LORD JUSTICE ALDOUS
LORD JUSTICE MANCE
and 
LORD JUSTICE LATHAM

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Between :

	PANDUIT CORPORATION	Claimant/
Appellant	
	- and -		
	
BAND-IT COMPANY LIMITED
	Defendant/
Respondent	

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(Transcript of the Handed Down Judgment of
Smith Bernal Reporting Limited, 190 Fleet Street
London EC4A 2AG
Tel No: 020 7421 4040,  Fax No:  020 7831 8838
Official Shorthand Writers to the Court)
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Henry Carr QC and Graham Shipley (instructed by Gouldens ) for the Appellants
Tom Mitcheson (instructed by Linklaters ) for the Respondents

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Judgment
As Approved by the Court

Crown Copyright ©

Lord Justice Aldous:

1.	The patentees of patent No. 2260158, Panduit Corporation, appeal against the judgment of Mr Peter Prescott QC, sitting as a deputy judge of the Patent’s County Court.  In that judgment he held the patent was invalid upon the ground of obviousness; but if it had been valid, it would have been infringed by Band-It Company Ltd.  
The Patent
2.	The patent has a priority date of 18th March 1991.  It concerns an invention entitled “Selectively coated cable tie”.  As the specification states, it relates to coated cable ties for fastening objects in a bundle.
3.	The basic idea can be seen from the four figures appended to the specification.
4.	

5.	The cable tie 10 shown in figure 1 surrounds cables 11.  The locking head 12, which is described in detail in US Patent No. 4, 399, 592, includes a metal ball which is not shown.  The strap is made of metal and plastic.  As shown in the cross-sectional view of figure 4, the metal part 18 is part-coated with plastic, 14, 16, 20, 22.
6.	The patent gives this background of the invention.  
“Prior metal ties have utilized a nylon coating over the entire surface of the cable tie strap to protect objects that come into contact with the tie from abrasion by the sharp edges of the metal tie.  Coated metal ties do not require the relatively expensive manufacturing step of forming a smooth radius on the sharp edges of each tie after it is slit from stock, thus decreasing the manufacturing cost of the coated ties.  
Coating the entire strap portion of a ball-lock cable tie of the type disclosed in US Patent No. 4, 399, 592 significantly degrades the loop tensile strength of the ball-lock tie.  Thus, there is a need for a means of coating a metal ball-lock cable tie with nylon to protect the objects to be bundled by the tie from abrasion by the edges of the tie while maintaining the locking effectiveness of the ball-lock cable tie.”	
7.	The object of the invention is stated to be the provision of a cable tie having coated lateral edges to protect objects that come into contact with them so that the coating does not interfere with the effectiveness of the locking mechanism of the tie.  That is achieved by the construction specifically shown in the figures and claimed in the claims.  They are in this form.
“1.  A selectively coated cable tie, comprising:
a strap having coating means for covering lateral sharp edges of the strap to prevent abrasion of objects that come into contact with the edges of the tie; and 
a locking head secured to a first end of the strap having locking means for locking a second end of the strap to the head; wherein the coating means does not cover an uncoated longitudinally extending medial portion of the strap which is aligned with the strap locking means in the head and is disposed on a side of the strap that engages the locking means such that the locking means of the strap does not engage the coating means when the second end of the strap is locked within the head of the strap, wherein the coating means covers the entire length of the lateral sharp edges of a portion of the second end of the strap contained within the locking head when the strap is locked within the locking head.
2.	A tie as set forth in claim 1, wherein the strap is formed of metal.
3.	A tie as set forth in claim 1, wherein the locking means includes a locking ball.   
4.	A tie as set forth in claim 1, wherein the coating means is a  nylon coating.  
5.	A tie as set forth in claim 1, wherein the coating means covers the entire surface of the strap, except for the uncoated longitudinally extending medial portion and the distal ends of the strap.  
6.	A tie as set forth in claim 1, wherein the coating means only covers lateral edges of the strap.  
7.	A selectively coated cable tie substantially as hereinbefore described with reference to the accompanying drawing.
8.	I will come later to the judgment, but will first comment on the witnesses who gave evidence.  On behalf of the claimants, the evidence fell into two categories.  First, expert evidence given by Dr Williamson.  He was described by the judge as “a completely honest witness”, but the judge felt he was somewhat like an advocate.  He was extremely well qualified in tribology and, although having a lifetime’s experience advising various branches of industry including the electrical connection and wiring industry, he did not claim that he had ever been called upon to design a cable tie, or to advise a person who was doing that.  The judge concluded that he was not representative of the notional person skilled in the art and that his opinion as to what was obvious had been influenced by the secondary evidence.  The judge stated that he was not satisfied that Dr Williamson appreciated the correct legal question.  It was for those reasons the judge did not rely upon his evidence as to whether the invention was obvious.  
9.	The second category included the secondary evidence.  That evidence was given by employees or ex-employees who had worked for Panduit between 1980 and the middle 1990s.  They gave evidence as to what was generally known, their thinking and the events that happened in Panduit.  The judge made no adverse comment on them as witnesses.  
10.	Band-It called Mr Billing to give expert evidence.  He was described by the judge as a “very fair witness”.  But he did not claim to have any practical experience of cable ties, let alone the conditions under which they would be used in the field and therefore was not representative of the notional skilled person.  The judge also concluded it was unclear as to how much of his expert report was his own work and how much was owed to the opinions and efforts of others, including Band-It’s managing director and their solicitors.  It was for those reasons that the judge rejected Mr Billings’ evidence as to what was obvious.  
11.	Band-It also called Mr Dodd, who was Band-It Company Limited’s managing director.  His experience was in sales and marketing, rather than in design and manufacturing.  The judge rejected his evidence on infringement upon the basis of his observations during cross-examination.   He said - “Having observed him under cross-examination I no longer find it [the evidence] at all persuasive.”
12.	Mr Blanks also gave evidence.  He had since 1993 been the product design manager and head of UK design at Hellermann Tyton which is a competitor of Panduit.  He described how Hellermann came to produce their design of a tie which was partly coated with plastic which they first marketed in 1997.  The judge held that Mr Blanks’ evidence did not of itself prove Band-It’s case because there were grounds for supposing that Mr Blanks was of an inventive turn of mind. 
The Judgment
13.	The judge dealt at considerable length with the law.  As no criticism was made of the judge’s recitation of the law, it is sufficient that I summarise his approach.  He reminded himself of the need to avoid hindsight and that obviousness had to be judged through the eyes of the skilled person.  With that in mind he referred to the speech of Lord Herschell in Vickers Sons & Co Ltd v Siddell (1890) 7 RPC 292 at 304 and that of Lord Diplock in Techonograph Printed Circuits v Mills & Rockley (Electronics) Ltd [1972] RPC 346.  He also referred to Hallen Co. v Brabantia (UK) Ltd [1989] RPC 307 and [1991] RPC 195 for the proposition that foresight of commercial success on the part of the notional skilled person was not the right test as it was enough if the claimed solution would have been obvious to him, even though there would be other solutions he might prefer to concentrate on and take further.  The judge also reminded himself of what Sir Donald Nicholls V.C. had said in Monlycke A.B. v Proctor & Gamble Ltd [1994] RPC 49 at 112 about the importance of evidence.  He went on to adopt the structured approach advocated by Oliver LJ in Windsurfing International Inc. v Tabur Marine (G.B) Limited [1985] RPC 59 at 73.  
14.	In view of the criticism of the judgment by Mr Carr QC, counsel for Panduit, I will set out the relevant parts of it, with the paragraphs identified by letters for convenience of reference.
“Step 1: the inventive concept.
(a) For present purposes it is convenient to go straight to claim 3, because this requires the presence of a locking ball; and if it was not obvious to come up with the concept of claim 3, I do not see how it could be obvious to come up with the concept of claim 1, since there would be no point in omitting the coating in the locking zone if there was no locking ball.
(b) Thus the inventive concept may be stated shortly as follows:  ‘Have a protective coating on the strap edges so that they won’t abrade the cables, but don’t have any coating on the locking zone [i.e. the part of the strap where the locking ball engages the strap]’.
Step 2: assuming the mantle of the normally skilled but unimaginative addressee.
(c)  In my judgement the person skilled in the art in this case would be an engineer wishing to design a cable tie.  Such a person would, in this country, typically have an H.N.D. or similar qualification and some practical experience in the cable tie industry.  If he needed to use a specialist technology (such as plastic coating) he would consult a specialist manufacturer for that purpose.
(d)  As part of his common general knowledge, the skilled person would know about the main types of cable tie available on the market, and in my judgement he would know about the Panduit metal ball-lock tie of the kind first disclosed in the U.S. patent.  He would know that there was a demand for plastic-coated cable ties (one such being Panduit’s MS strap) because customers feared that the relatively sharp edges of the all-metal tie could abrade the cables.  In other words he would perceive that coating a metal tie with a suitable plastic could reduce the risk of abrasion.  He would also know that it was desirable to achieve a good tensile strength when the tie was wrapped around the cables, and this would depend on the effectiveness of the locking-head.
…
Step 3: identifying the differences between the prior art and the alleged invention.
(e)  In my judgement the closest point of departure, for present purposes, is the all-metal ball-lock cable tie, although the skilled person also knew that coating metal cable ties with plastic could be desirable in principle.  The difference, then, is that plastic or some other suitable coating is present at least on the edges of the tie but not in the locking zone.

Step 4: ascertaining whether the differences would have been obvious to the skilled person.
(f)  In order to arrive at the inventive concept the notional skilled person would have had to take two steps.  First, to try putting a coating on the strap as a whole and seeing how that behaved.  Secondly, on finding that the tensile strength of the tie was degraded, deciding to remove or omit the plastic from the locking zone.
(g)  In my judgement the first step, of itself, was plainly obvious.  I do not think it is in dispute.  Dr Williamson (first report, paragraph 53(d)) said that “it was apparent for some time after the introduction of the MLT that it was desirable to have a coated version”.  Not do I believe that the skilled worker would be deterred from taking the first step through fears that the plastic would prevent the locking mechanism from working.  As Dr Williamson said in the same passage, “[it would have seemed] obvious to me that a ball lock would get a better grip on soft plastic than on unyielding steel”.  What he found surprising was that, when tried, it was worse.
(h)  I therefore envisage the skilled, normally diligent but unimaginative person setting to work.  He coats his strap all over with plastic (more accurately, he gets a specialist contractor to do it for him).  He then investigates its behaviour, and since he knows that the tensile strength of a cable tie (i.e. the efficacy of its locking-head) is a relevant attribute, he investigates that.  He finds, either by testing it on a machine or simply by pulling it with his hands that the tensile strength is severely degraded.  So far, I believe that nothing I have described is a matter of contention, but in any case I hold that that is what he would have done.  The question is, what next?
(i)  It is said by Panduit that the skilled person would give up, and try to devise a better kind of locking head, or perhaps go down some other route.  It is here that it is vital to bear in mind the distinction between the obviousness of a given technical result and obviousness that it would produce commercial success.  It may be that the skilled person would think: “My purpose to get a tensile strength which is a good as in the bare metal tie, about 250 pounds, for I believe the customers will not settle for less.  Since this thing looks too unpromising, I must try a different approach.”  But, if I have directed myself correctly in law, that would not be relevant.  What signifies is, not whether the skilled man would think it commercially worthwhile, but whether it would be apparent to him how to get a technically better performance – how to achieve some improvement.
(j) In my judgement, the skilled worker, although unimaginative, would not be a fool.  He would be capable of logical if routine thought.  He would think to himself along these lines:  “It worked fine when there was no plastic; it doesn’t with the plastic there; therefore it must be the plastic that is causing the problem”.  He would know that, in a ball-locking tie, it is the contact between the ball and the strap which provides the main locking force, even if by no means all of it.  It would therefore be obvious to him to machine away the plastic in the ball-locking zone.  When he did, he would observe a materially improved result.  True, it might not be good enough to induce him or his employer to take the project to a commercial conclusion.  But he would have arrived within the claim.
(k)  In case it matters, I hold that it would also be obvious to him that, if he wanted to, he could produce a tie with no plastic in the locking-zone by not coating that zone in the first place.  He would just have to ask his specialist plastic contractors and they would know how to do it.
(l)  There are no technical reasons, drawn to my attention by the expert witnesses, which would cause me to differ from the above conclusion.  It is true that if the skilled person did not machine away the plastic sufficiently, a thin and invisible layer might remain which would behave as a lubricant.  But I do not believe this would defeat him.  He would then appreciate that he had not yet got a sufficiently ‘clean’ surface, and proceed accordingly.
(m)  If Dr Williamson’s expert report is read with attention it will become apparent, I believe, that he is doing two things.  First, merely stating that he is quite unable to see how the invention could be said to be obvious; but without providing any corroborating technical reasons, save what I am about to refer to.  Secondly, he is himself relying on what the courts have called the ‘secondary’ evidence.  In effect, he is saying, the invention would have been introduced long before if it has been obvious, and skilled engineers at Panduit failed to find the solution until Mr Caveney came up with it.  I have paid careful attention to the evidence of Dr Williamson but in the end it has not persuaded me that the invention was non-obvious.
(n)  In my judgement the secondary evidence is not such as to lead one to revise the above prima facie conclusion.  I accept that at least some engineers in Panduit who set out to investigate a plastic-coated ball-lock cable tie did not produce a selectively coated version.  But I cannot treat this as very persuasive, let alone controlling evidence unless I am reasonably satisfied that their approach properly represented that of the notional person skilled in the art, for I have to bear in mind that the question is, not whether it would have been obvious to him that a commercially promising product could be obtained by omitting the plastic in the locking zone, but that he could get a technical improvement.  Panduit’s objective, initially, was to produce a plastic-coated ball-lock cable tie which would have a tensile strength equal to that of the existing metal product.  In fact, they afterwards abandoned that goal as too ambitious, and settled for less.  See the cross-examination of Mr Chopp, day 1 pages 66-72.  It may have been an astute commercial move on the part of Panduit to appreciate that the degraded performance would nevertheless be acceptable to a number of customers. It may also be, for all that I know, that having arrived at the concept of a selectively coated tie a manufacturer who sought commercial success would devote efforts to improving the design of the locking head; but such a design is not disclosed in the patent and I do not believe it can be relevant consideration.  I am quite unsatisfied that the secondary evidence adds anything to the case.
(o)  If the invention of claim 3 was obvious, as I believe it was, it seems to me that the features of claim 4 to 6 add nothing of relevance.  I am not persuaded that the invention claimed in the omnibus claim (claim 7) was obvious.
Conclusion.
(p)  I therefore hold that the Band-It cable ties complained of fall within claims 1-5 of the patent, but that the invention of all of those claims was obvious.”
The Appeal
15.	Mr Carr submitted that the judge had gone wrong both in principle and result. He collected together his submissions under four topics.  First, he submitted that the judge had failed to apply his mind to the evidence or lack of evidence with the result that he reversed the onus of proof.  Second, the judge had fallen into the trap of hindsight reasoning.  Third, the judge had not properly put on the mantle of the skilled person.  Fourth, the judge had failed properly to consider the secondary evidence.  Mr Mitcheson submitted that the judge had come to the right conclusion for the right reasons.  There was no error and the conclusion reached was correct upon the evidence.  
16.	Mr Mitcheson reminded us that this Court should be cautious in differing from the judge’s evaluation of what was obvious.  As Lord Hoffmann in Biogen Inc. v Medeva [1997] RPC 1 at 45 said:
“It is because specific findings of fact, even by the most meticulous judge, are inherently an incomplete statement of the impression which was made upon him by the primary evidence.  His expressed findings are always surrounded by a penumbra of imprecision as to emphasis, relative weight, minor qualification and nuance (as Renan said, la vérité est dans une nuance), of which time and language do not permit exact expression, but which may play an important part in the judge’s overall evaluation.  It would in my view be wrong to treat Benmax as authorising or requiring an appellate court to undertake a de novo evaluation of the facts in all cases in which no question of the credibility of witnesses is involved.  Where the application of a legal standard such as negligence or obviousness involves no question of principle but is simply a matter of degree, an appellate court should be very cautious in differing from the judge’s evaluation.”
17.	Mr Carr submitted the invention in this case was very simple and that the words of Lord Herschell in Vickers Sons & Co Ltd v Siddell at page 304 were particularly apt:
“If the apparatus be valuable by reason of its simplicity there is a danger of being mislead by that very simplicity into the belief that no invention was needed to produce it.  But experience has shown that not a few inventions … have been of so simple a character that once they had been known it was difficult … not to believe that they must have been obvious to everybody.”	
18.	To similar effect was the speech of Lord Russell in Non-Drip Measure Co Ltd v Strangers Ltd [1943] 60 RPC 135 at 142:
“Whether there has or has not been an inventive step in constructing a device for giving effect to an idea which when given effect to seems a simple idea which ought to or might have occurred to anyone, is often a matter of dispute.  More especially is this the case when many integers the new device are already known.  Nothing is easier than to say after the event, the thing was obvious and involved no invention.  The words of Molton LJ in British Westinghouse v Brawlick may well be called to mind in this connection: ‘I confess’ (he said) ‘that I view with suspicion arguments to the effect that a new combination, bringing with it new and important consequences in the shape of practical machines, is not an invention, because when it has once been established, it is easy to show how it might be arrived at by starting from something known, and taking a series of apparently easy steps.  This ex post facto analysis of invention is unfair to inventors and, in my opinion, it is not countenanced by English patent law …’”	
19.	To that Mr Carr added this often cited extract from the speech of Lord Diplock in Technograph Printed Circuits v Mills & Rockley (Electronics) Ltd [1972] RPC 346 at page 342:
“The cross-examination of the respondent’s expert followed with customary skill the familiar ‘step by step’ course.  I do not find it persuasive.  Once an invention has been made it is generally possible to postulate a combination of steps by which the inventor might have arrived at the invention that he claims in his specification if he started from something that was already known.  But it is only because the invention has been made and has proved successful that it is possible to postulate from what starting point and by what particular combination of steps the inventor could have arrived at his invention.  It may be that taken in isolation none of the steps which it is now possible to postulate, if taken in isolation appears to call for any inventive ingenuity.  It is improbable that this reconstruction a posteriori represents the mental process by which an inventor in fact arrived at his invention, but, even if it were, inventive ingenuity laid in perceiving that the final result which was the object of the inventor to achieve was attainable from the particular starting point and in his selection of the particular combination of steps which would lead to that result.”	
20.	Mr Carr reminded us that almost invariably expert evidence was needed to discharge the onus upon the person alleging invalidity of a patent.  In support he referred to the guidelines given by Sir Donald Nicholls VC in Monlycke A.B. v Proctor & Gamble Ltd [1994] RPC 49 at 112.  
“The Act requires the court to make a finding of fact as to what was, at the priority date, included in the state of the art and then to find again as a fact whether, having regard to that state of the art, the alleged inventive step would be obvious to a person skilled in the art.
In applying the statutory criteria and in making these findings the court will almost invariably require the assistance of expert evidence.  The primary evidence will be that of the properly qualified expert witnesses who will say whether or not in their opinions the relevant step would have been obvious to a skilled man having regard to the state of the art.  All other evidence is secondary to that primary evidence.  In the past, evidential criteria may have been useful to help to elucidate the approach of the common law to the question of inventiveness.  Now that there is a statutory definition, evidential criteria do not form part of the formulation of the question to be decided.
In the nature of things, the expert witnesses and the court are considering the question of obviousness in the light of hindsight.  It is this which may make the court’s task difficult.  What with hindsight seems plain and obvious often was not so seen at the time.  It is for this reason that contemporary events can be of evidential assistance when testing the experts’ primary evidence.  For instance, many people may have been industriously searching for a solution to the problem for some years without hitting upon the allegedly obvious invention.  When this type of evidence is adduced the court can quickly find itself caught up in an investigation of what was or was not obvious to certain identified individuals at certain dates during the history of the development of the product or process involved.  This gives rise to complications because the state of knowledge of these individuals, although skilled, may not correspond to the statutory definition of the state of the art.  A particular inventor may have been unaware of some aspect of the state of the art as defined in section 2(2) and may therefore have generally taken what was actually an inventive step, but nevertheless be unable to claim a patentable invention since the step was, in the terms of the statute, obvious.  Further, this type of evidence invites the court to speculate whether particular individuals were of an inventive disposition, because the earlier making of the same invention by another or others does not necessarily mean that at a later date the invention was obvious.  Yet again, evidence of the commercial success of the invention can lead into an investigation of the reasons for this success; there may be commercial reasons for this success unrelated to whether this invention was or was not obvious in the past.
Secondary evidence of this type has its place and the importance, or weight, to be attached to it will vary from case to case.  However such evidence must be kept firmly in its place.  It must not be permitted, by reason of its volume and complexity, to obscure the fact that is no more than an aid in assessing the primary evidence.”	
21.	Sir Donald Nicholls V.C. in Monlycke referred to the evidence of experts as the primary evidence.  As I have said, the judge rejected the evidence of both experts as to what was obvious and therefore there was no primary evidence.  That did not mean Band-It could not discharge the onus on them, but their task became difficult. In the present case the judge did not consider whether and how that onus was discharged.  He concluded in paragraph (f) that “to arrive at the inventive concept the notional skilled person would have had to take two steps.  First, to try putting a coating on the strap as a whole and seeing how that behaved.  Secondly, on finding that the tensile strength of the tie was degraded, deciding to remove or remit the plastic from the locking zone.”
22.	In my view Mr Carr is right that the judge started from knowledge of the invention and from that postulated, without expert evidence, that those were the two steps that would have been contemplated by the skilled person in 1991.  He assumed the route.  He then concluded it was obvious and when he came to the secondary evidence, he said in paragraph (n) – “In my judgment the secondary evidence is not such as to lead one to revise the above prima facie conclusion.”  In so doing he appears to have failed to have kept in mind that he had to decide whether Band-It had established that the invention was obvious.  That required him to consider the evidence as a whole.  The secondary evidence might not rebut a conclusion of obviousness, but it would have been, or at least could have been, relevant when coming to a conclusion as to whether the invention was obvious in the absence of primary evidence.  
23.	The main attack upon the judgment came in Mr Carr’s second submission.  The second step of Windsurfing requires the judge to adopt the mantle of the skilled person.  This is particularly important where, as in this case, the attack upon the patent is based upon what was generally known in the art.  
24.	In paragraph (d) of the judgment, the judge held that the skilled person would know about “the main types of cable ties available on the market” and the Panduit metal ball-lock tie referred to as the MTL.  Although the judge failed to identify the main types that were available, the evidence established that they were either completely coated with plastic or were uncoated. 
25.	Mr Carr submitted, rightly in my view, that the judge had failed to decide whether the skilled person believed that there were reasons for coating and, if so, what they were.  He should, Mr Carr submitted, have found that, as of 1991, the skilled person knew that abrasion could be dealt with by edge dressing and that the real reasons for coating a tie were in the words of Mr Dodd – “to make the tie easier to handle in very cold temperatures, often encountered, e.g. in the North Sea – in freezing conditions exposed skin tends to stick to bare metal; to prevent galvanic reaction between the stainless steel tie and a different metal: chiefly the galvanised steel trays and ladders which hold the cables and cable ties; and, for the thicker coatings, in certain circumstances the coating may prevent abrasion of the cable being tied.”  
26.	Mr Billings (Evidence 2 at pages 170-173) accepted that the “well-known reasons for having a fully coated tie were protection of hands in cold weather, prevention of galvanic reaction and the perceived avoidance of abrasion.”  He stated that protection from corrosion was another reason.  
27.	Mr Blanks said in his witness statement that – “coated ties were originally developed to avoid corrosion …, to prevent galvanic reaction between the body of the tie and cables/ladders … another advantage is that they make metal ties easier to handle in cold temperatures … there is a perception in the market place that coated ties prevent or reduce abrasion.”  
28.	It followed that there was agreement amongst those witnesses who gave evidence as to the reasons why the trade had produced coated ties.  It was done to provide ease of handling in cold temperatures; to avoid galvanic reaction; to avoid abrasion or perhaps the perceived need to avoid abrasion and to avoid corrosion.  That being so, it was necessary for the judge to consider the fourth Windsurfing step with those reasons in mind.  They formed part of the mantle of the skilled person through whose eyes obviousness had to be judged.  
29.	When carrying out the third Windsurfing step the judge rightly identified the difference between the prior art and the well-known MTL ties as being the partial coating feature (see paragraph (e) of the judgment).  
30.	The fourth Windsurfing step requires the court to consider whether the differences were obvious without having in mind the invention.  In the present case the reasoning of the judge in paragraphs (f) to (k) adopts the two step approach to which I have referred.  First, the judge concluded it was obvious to try putting a coating on the metal Panduit MTL tie.  Second, the failure to produce a satisfactory tie would be solved by machining away part of the plastic coating.  His reasoning is in my view a classic ex post facto analysis which was made without recourse to evidence.  He moved to the claimed invention by two steps, neither of which were established by the primary evidence to be obvious.  They of course could be postulated because the destination, the invention, was known to him.  
31.	There were on the market at the time fully coated and fully uncoated ties.  The question to be decided was: was it obvious to move from the uncoated MTL to a partially coated one?  As the judge held on page 6 of his judgment, the skilled person would realise that the coating would interfere with the effectiveness of the locking mechanism by making it hard to thread or by the plastic layer on the other side to the ball slipping.  The skilled person would also have in mind that coatings were applied to help handling in cold temperatures, to avoid galvanic reaction, to avoid corrosion and abrasion.  Against that background it was not right for the judge to conclude, in the absence of primary evidence, that it was obvious to coat the MTL tie let alone to do it partially.  The evidence of Dr Williamson, relied on by the judge, in paragraph (g) of the judgment, when read as a whole, did not support that view.  In paragraph 53 of his witness statement Dr Williamson observed that there had been a commercial demand for coated ties which had been met by the fully coated MS strap.  Uncoated metal ties had been available from the early 1980s and it was odd that the coated version had not been produced if it was obvious.  Whilst a coated version of the MTL was desirable, it was not obvious partially to coat.  I accept the judge’s conclusion that Dr Williamson was not representative of the skilled person and therefore it would not be right to rely upon that conclusion.  That being so, there was no justification for the judge relying on a part of paragraph 53 of his witness statement without taking into account the rest of that paragraph.  
32.	In my view the reasoning of the judge in paragraphs (g) and (h) is flawed by his failure to adopt the mantle of the skilled person.  If he had done so, he would have had in mind the reasons why coatings were applied to ties.  He would have concluded that the skilled person would have had in his mind that removal of part of the coating would have upset the very purpose of putting it on.  It would have exposed part of the metal which could affect hands in cold weather, produce galvanic reaction and corrosion.  It was against that background that the judge had to answer the fourth step of Windsurfing.  In the absence of any primary evidence, there was in my view no basis for the judge concluding that Band-It had discharged the onus on them.  The obvious way to avoid abrasion was to improve edge dressing as coating would not meet the needs for which coated ties were made.      
33.	As Sir Donald Nicholls VC pointed out in Monlycke secondary evidence can be relevant, but it must be kept in its place.  It must not “obscure the fact that is no more than an aid in assessing the primary evidence.”  In the present case there was no relevant primary evidence and the secondary evidence was unlikely to be able to discharge the onus on Band-It.  The judge did not say that it did.  He only held that the secondary evidence had not rebutted the conclusion he had reached.  Even so, Mr Mitcheson submitted that the secondary evidence established that the invention was obvious.  Mr Carr submitted that it pointed the other way.  
34.	The first category of secondary evidence was that given by Panduit’s employees as to what they did.  Mr Chopp and Mr Mohr were continuously looking to reduce or prevent abrasion with the MLT.  They first developed the fully radiused edged form and in the mid 1980s started looking at coating the MLT with Nylon 11.  They made prototypes of fully coated versions which were rejected because of slippage.  One suggestion to overcome this was a spiked ball as the locking mechanism.  They did not think of producing a partially coated version.  It was their view that if the invention had been obvious, they would have thought of it.  Clearly that evidence could support a conclusion that the invention was not obvious, but it was open to the observation that they may have missed the obvious.  
35.	Panduit disclosed documents showing what a Mr Sorenson did in August 1988.  His witness statement was before the court pursuant to a Civil Evidence Act notice, but he was not called to give evidence.  The documents showed the results of his research “To determine loop tensile strength of nylon 11 coated MTL clamps.”  It seems from the documents that one of the ties that he tested had part of the nylon coat ball-side, scraped away.  The loop tensile strength results were 132, 27 and 70 lbs which showed that the ties tested were commercially unsatisfactory and varied widely in strength.  Mr Mitcheson submitted that Mr Sorenson was an example of an uninventive person carrying out workshop modifications.  The result of his work was production of a tie falling within the claims of the patent.  The fact that the tensile strength tests were bad was irrelevant as the claim did not contain any limitation as to tensile strength.  Mr Carr submitted that it seemed unlikely that Mr Sorenson was representative of the type of skilled person concerned and there was nothing to suggest that he realised that removal of part of the nylon coating would mean that at least 3 of the reasons for applying the coating would be removed.
36.	It was unfortunate that Mr Sorenson was not called to give evidence so that his experience could have been explored.  In the circumstances it is difficult to draw any clear conclusion as to whether what he did was illustrative of the acts of a notional skilled person or a person who did not have the relevant mind-set.
37.	Mr Mitcheson also relied upon the pleaded prior use called the Zuccon prior use.  It was not relied on by the judge as part of the secondary evidence, but it appears to have been made in 1988.  It was not established to form part of the state of the art, but it probably fell within claim 1.  There is doubt about what happened as the only witness called to give evidence, Mr Zuccon, was so vague that the judge held – “I do not believe he had a proper recollection of what transpired 12 years ago.”  
38.	Mr Blanks described in his witness statement how in 1996 his company sent uncoated MLT samples to be coated.  He said that upon receipt of the coated samples, it was immediately clear to him that the plastic coating was interfering with the tie function.  To overcome that they machined away part of the plastic.  That he said was completed before March 1997 when he saw the patented version sold by Panduit.  That evidence, the judge was asked to infer, supported the conclusion that the invention was obvious and that the judge’s two step approach was not hindsight reasoning.  
39.	Panduit applied for disclosure by Mr Blanks’ employers of the documents that Mr Blanks had looked at before preparing his witness statement.  Disclosure was refused, but Mr Blanks produced a document dated 26th March 1997 which he had looked at before making his statement.  It was written by him.  It stated:
“The competitor product launched by Panduit recently, so is technically achievable.  Require samples of Panduit tie to evaluate how they have overcome functional/technical problems associated with leaving an uncoated track to allow the ball bearing to function.  Action DA to order Panduit product and obtain samples of specialist tapes/chemical masking for further trials on existing MBTH product, within next 4 weeks.”
The document goes on to deal with the technical problems envisaged for coating.  
40.	As the judge recorded at page 16 of his judgment, Mr Carr attacked the credibility of Mr Blanks.  The suggestion was that the coating trial had been carried out after he had seen the Panduit partially coated tie in March 1997, not in 1996.  Unfortunately the judge did not deal with this submission.  If he had he would have referred to a number of unsatisfactory answers that Mr Blanks gave in cross-examination.  Even so, it would not be right for this Court to conclude that Mr Blanks was not giving his evidence according to his recollection.  However it is of interest that no document was produced which supported his evidence that he thought of partial coating before seeing the Panduit partially coated MLT.  The document that was produced can be read as suggesting to the contrary.  In any case, as the judge held, Mr Blanks was of an inventive turn of mind.  It follows that even if he had thought of partially coating in 1996, that did not indicate that the invention was obvious.  
41.	The secondary evidence also included the evidence as to what Band-It did.  They were aware of the uncoated version in the mid 1980s.  It seems that they became aware of the partially coated MTL in the summer of 1997.  On 28th August 1997 Mr Dodd wrote to the president of Band-It USA explaining that they were concerned about competition from two partially coated locking ties.  He went on:
“So far we have managed to hold things more or less together, with the promise of our own proprietary self-locking tie and application tool, available later this year.  However, according to our conversation this week, the testing of our new product does not appear suitable for coating.  I am very afraid that this situation will leave us at a great disadvantage to other manufacturers.  If this is the case, as I proposed, the ideal answer may be to produce our own Panduit “clone”.  We know this type of product is well accepted by the market and can be coated.  If we reached a positive decision to move in this direction, I suggest we make this a fast track project, as every day we are left out of this market will make our task to re-establish our position all the more difficult.
As you know I consider this whole issue to be absolutely vital to us remaining a key player in the electrical accessories market.  I would be more than pleased to be part of a discussion with everyone in Denver to debate this most important issue, providing you consider this proposal advantageous.”
42.	In his cross-examination Mr Dodd accepted that the Band-It Group had an engineering department, and that they had not thought of a partially coated ball-lock tie before they had seen the Panduit sample.  Mr Carr submitted that this was an example of persons skilled in the art not arriving at what was said to be obvious, although it would have been in their interest to do so.  That supported the view that the invention, although simple, was not obvious.  
43.	Mr Carr submitted that the secondary evidence, when taken as a whole, showed that the invention had not been obvious to a number of notional skilled persons in the art.  Mr Mitcheson submitted to the contrary.  He submitted that the reason for the delay in producing a partially coated version of the MTL was that the patent covering the ball-lock had kept manufacturers from producing a similar device until a way of using a ball-lock, which did not infringe the Panduit ball-lock patent, had been devised in the early 1990s.  Thus the most pertinent evidence was what Mr Sorenson, Mr Blanks and Mr Zuccon did.  That evidence he submitted, supported the judge’s reasoning and conclusion.
44.	It is difficult, in the absence of findings of fact as to the secondary evidence, for this Court to come to a concluded view as to its overall effect of it.  My impression is that it could support the submissions of Panduit that – “if it had been obvious to partially coat, that would have been done in the mid 1980s.”  However I am clear that it did not establish that the invention was obvious.  That being so, the relevant evidence did not support the judge’s conclusion.  
45.	Once it is appreciated that the skilled person would have had in his mind that the reasons for coating were to avoid difficulties in cold temperature, to avoid corrosion and galvanic reaction and the perceived difficulty of abrasion, it is clear that the judge’s reasoning cannot be supported.  In the absence of relevant evidence, I have come to the conclusion that Band-It did not establish that the patent was obvious.  It follows that the attack on the patent must fail and this appeal must be allowed.  

Lord Justice Mance:

46.	I agree with the reasons given and the conclusion reached by Aldous LJ.
47.	I was at one point troubled by the respondents’ submissions based on the test of obviousness.  My Lord put the matter in this way at first instance in Hallen v Brabantia [1989] RPC 307:
“The word “obvious” in section 3 [of the Patents Act 1977] is I believe directed to whether or not an advance is technically or practically obvious and not whether it is commercially obvious. …. The prize for a good commercial decision or idea is a head start on the competition and not a monopoly for twenty years.”
48.	In this court at [1991] RPC 195, 213, Slade LJ quoted from the Windsurfing case [1985] RPC 59, to which my Lord has referred, where Oliver LJ said this at page 72:
“What has to be determined is whether what is now claimed as invention would have been obvious, not whether it would have appeared commercially worthwhile to exploit it.”
Slade LJ then said:
 “We therefore agree with the judge that the word “obvious in section 3 is not directed to whether an advance is “commercially obvious”.
49.	So, it is argued that, in this case, the only consideration that held anyone back from devising and producing a partially coated metal ball-lock tie (“MTL”) was that it would not have appeared commercially worthwhile to do so.
50.	I have come to the conclusion, however, that this is a case, like Dyson Appliances  Ltd. v Hoover Ltd. [2001] EWCA Civ 1440, where the critical factor was “mindset”.  Sedley LJ said in Dyson at paragraph 87 that:
“…. the perceived limits of technical practicability are a matter of mindset, and that mindset is characteristically affected by awareness of need, of which commercial potential is both a function and an index”
and at paragraph 88 that:
“If then the intellectual horizon of practical research and innovation is in part set by the economic milieu, commercial realities cannot necessarily be divorced from the kinds of practical outcome which might occur to the law’s skilled addressee as potentially worthwhile.”
51.	With some residual doubt, I consider that the same applies in the present case. No-one would have considered devising or producing a partially coated metal ball-lock tie, because the whole idea of coating was seen as being to coat the tie as a whole.  The reasons were practical reasons - to facilitate handling in cold weather, to avoid galvanic reaction and corrosion, as well as to eliminate any risk or apprehension of sharp edges.  A partially coated tie would not satisfy these largely technical aims.  Once it became apparent that a completely coated metal ball-lock tie would not do, because of the adverse effect on the ball-lock, the natural course was to revert to a wholly uncoated tie or to devise some other form of locking device that would work with coating.  For these practical reasons, the idea of a partially coated metal ball-lock tie was not obvious.  That the market might be satisfied with lesser technical performance, in particular the risk of galvanic reaction and corrosion and of coldness to touch in freezing conditions, was only demonstrated by Panduit’s invention.
Lord Justice Latham:
52.	I agree that the appeal should be allowed for the reasons given by Lord Justice Aldous. 
Order: Appeal allowed with costs here and below; interim payment of costs in the sum of £150,000; order as agreed between the parties; order made in paragraph 4 without any requirement for exhibiting the relevant documents; paragraph 6 will be replaced by an order in this form:
“The question as to whether the first defendant can rely on, and if so establish, a defence pursuant to section 62(1) of the Patents Act 1977 be referred to the Master or Judge who hears the inquiry or account.”
(Order does not form part of the approved judgment)