Neutral Citation Number: [2009] EWHC 82 (Ch)
Case No: CH/2008/APP/0275
IN THE HIGH COURT OF JUSTICE
CHANCERY DIVISION

Royal Courts of Justice
Strand, London, WC2A 2LL

Date: 23/01/2009

Before :

THE HONOURABLE MR JUSTICE HENDERSON
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Between :

	THE COMMISSIONERS FOR HER MAJESTY'S REVENUE & CUSTOMS	Appellants	
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	FLIR SYSTEMS AB	Respondent	

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Mr Kieron Beal (instructed by the Solicitor for HMRC) for the Appellants
Ms Valentina Sloane (instructed by Forbes Hall) for the Respondent

Hearing date: 26 November 2008
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Judgment
Mr Justice Henderson : 
Introduction
1.	The issue on this appeal is how four thermal imagers manufactured by a Swedish company, Flir Systems AB (“Flir”), should be classified for customs duty under the EU tariff regime contained in the so-called Combined Nomenclature.  
2.	In March 2007 the Commissioners for Her Majesty’s Revenue and Customs (“HMRC”) issued binding tariff informations (“BTIs”), following a review, which classified the imagers under heading 9025 19 20 90 as electronic thermometers.  Flir appealed to the VAT and Duties Tribunal (“the Tribunal”), contending that the correct classification was under heading 8525 80 30 00 as digital cameras, or alternatively under heading 9027 50 00 00 as instruments using optical radiations for measuring or checking quantities of heat.  The alternative contention had not been included by Flir in its grounds of appeal, and had not been considered in the written evidence prepared by the parties. It was raised for the first time in the skeleton argument of counsel for Flir, Ms Valentina Sloane.  However, the Tribunal allowed it to be advanced, and HMRC have not argued on the appeal to this court that they were wrong to do so. 
3.	The Tribunal (chaired by Dr John Avery Jones CBE, with Ms Roberta Johnson BSc as its other member) heard Flir’s appeal on 18 and 19 February 2008, and delivered their decision on 27 February (“the Decision”). They held that Flir’s alternative contention was correct, and therefore allowed the appeal. 
4.	HMRC now appeal to the High Court.  By virtue of section 11(1) of the Tribunals and Inquiries Act 1992, the appeal lies only on points of law. It follows that findings of fact by the Tribunal cannot be challenged, unless they disclose an error of law in the sense explained by the House of Lords in Edwards v Bairstow [1956] AC 14: see the well-known passages in the speeches of Lord Radcliffe at 33-36 and Viscount Simmonds at 30-31.
5.	The representation has been the same before me as it was before the Tribunal, with Ms Sloane appearing for Flir and Mr Kieron Beal appearing for HMRC. I am grateful to them both for their clear and helpful arguments.
The Legal Background
6.	A full account of the legal background to the EU customs tariffs, and the principles to be followed in their interpretation, was given by Lawrence Collins J (as he then was) in Vtech Electronics (UK) Plc v Customs & Excise Commissioners [2003] EWHC 59 (Ch) (“Vtech”). What follows is intended to be a relatively brief summary.  
7.	The EU is a contracting party to the International Convention on the Harmonised Commodity Description and Coding System, generally known as “the Harmonised System”.  The Convention requires that the tariffs and nomenclatures of contracting states conform to the Harmonised System, and all contracting states therefore use the headings and sub-headings of the Harmonised System.  The system is administered by the World Customs Organisation in Brussels, which publishes explanatory notes to the Harmonised System known as “HSENs”.  
8.	At Community level, the amount of customs duties on goods imported from outside the EU is determined on the basis of the Combined Nomenclature (“CN”) established by Article 1 of Council Regulation 2658/87 and Article 20.3 of Regulation 2913/92. The CN is re-issued annually. It comprises three elements:
(a) the nomenclature of the Harmonised System;
(b) Community sub-divisions to that nomenclature; and
(c) the preliminary provisions, additional section or chapter notes and footnotes relating to CN sub-headings.
9.	The CN uses an eight-digit numerical system to identify a product, the first six digits of which are those of the Harmonised System, while the two following digits identify the CN sub-headings, of which there are about ten thousand. Where there is no Community sub-heading, these two digits are “00”. There may also be ninth and tenth digits which identify further Community (TARIC) sub-headings, of which there about eighteen thousand. 
10.	Apart from the HSENs to which I have already referred, the European Commission also issues Explanatory Notes of its own to the CN which are known as “CNENs”.  
11.	The Court of Justice of the European Communities (“the ECJ”) has repeatedly stated that the decisive criterion for the tariff classification of goods must be sought in their objective characteristics and properties as defined in the wording of the relevant heading of the CN and of the notes to the sections or chapters of the CN.  The two categories of Explanatory Notes, that is to say the HSENs and the CNENs, are an important aid to the interpretation of the scope of the various tariff headings, but do not themselves have legally binding force.  The content of the Explanatory Notes must therefore be compatible with the provisions of the CN, and cannot alter the meaning of those provisions. See, for example, Case C-495/03 Intermodal Transports BV v Staatssecretaris van Financien, [2005] ECR I-8151, at paragraphs 47 and 48.
12.	Part 1 of the CN contains at Section 1A the General Rules for the Interpretation of the CN.  These General Rules are known as “GIRs”. Unlike the Explanatory Notes, they have the force of law (see Vtech at paragraph 16).
13.	So far as material, the GIRs provide as follows:
“Classification of goods in the Combined Nomenclature shall be governed by the following principles:
1. The titles of sections, chapters and sub-chapters are provided for ease of reference only; for legal purposes, classification shall be determined according to the terms of the headings and any relative section or chapter notes and, provided such headings or notes do not otherwise require, according to the following provisions.
2.
(a) …
(b) Any reference in a heading to a material or substance shall be taken to include a reference to mixtures or combinations of that material or substance with other materials or substances. Any reference to goods of a given material or substance shall be taken to include a reference to goods consisting wholly or partly of such material or substance. The classification of goods consisting of more than one material or substance shall be according to the principles of rule 3.
3. When, by application of rule 2(b) or for any other reason, goods are prima facie classifiable under two or more headings, classification shall be effected as follows:
(a) the heading which provides the most specific description shall be preferred to headings providing a more general description. However, when two or more headings each refer to part only of the materials or substances contained in mixed or composite goods or to part only of the items in a set put up for retail sale, those headings are to be regarded as equally specific in relation to those goods, even if one of them gives a more complete or precise description of the goods;
(b) mixtures, composite goods consisting of different materials or made up of different components, and goods put up in sets for retail sale, which cannot be classified by reference to 3(a), shall be classified as if they consisted of the material or component which gives them their essential character, in so far as this criterion is applicable;
(c) when goods cannot be classified by reference to 3(a) or (b), they shall be classified under the heading which occurs last in numerical order among those which equally merit consideration.
4. Goods which cannot be classified in accordance with the above rules shall be classified under the heading appropriate to the goods to which they are most akin.
5. …
6. For legal purposes, the classification of goods in the sub-headings of a heading shall be determined according to the terms of those subheadings and any related subheading notes and, mutatis mutandis, to the above rules, on the understanding that only subheadings at the same level are comparable. For the purposes of this rule, the relative section and chapter notes also apply, unless the context requires otherwise.”
14.	It can be seen that the General Rules quoted above provide a hierarchical set of principles, and if the correct classification can be ascertained at a given stage it is unnecessary to proceed any further.  
The Competing Classifications
15.	The competing classification headings are set out in paragraph 3 of the Decision, and I need not repeat them.  If the products in question fell within either of the headings contended for by Flir, they would be free of duty, whereas under the heading contended for by HMRC they would bear duty at the rate of 3.2%.
The Products
16.	The Tribunal heard factual evidence from Flir’s deputy service manager, Mr Kevin Saxton.  Mr Saxton holds an honours degree in electrical and electronic engineering, and had worked with Flir for the past eleven years.  In paragraphs 4 and 5 of his witness statement, he described the basic principles of thermography in the following terms:
“4. Thermal radiation is energy emitted from the surface of an object which is due to the object’s temperature above absolute [zero] which is -273ºC or -460ºF.  Hot objects emit more energy than cold objects.
5. Thermography, according to Flir Systems, is the science of acquisition and analysis of thermal information from non-contact thermal imaging devices. The energy from an object is radiated at different levels across the electromagnetic spectrum of which infrared is a part.  The infrared region can be sub-divided into two regions (in which Flir manufacture equipment for the thermography market): the mid-band is concerned with infrared spectrums from 3 to 5 microns … while the long wave ranges from 8 to 12 microns … . The majority of Flir cameras fall into the latter part of the infrared spectrum with the cameras that make up this appeal falling into the long wave.”
17.	The Tribunal also heard evidence from an expert witness retained by HMRC, Mr Bevan Clues, who is a chartered electrical engineer and a member of the Institution of Engineering and Technology.  In his written report he says that he has worked widely as a consultant since 1980 on the design, development, testing and installation of telecommunications systems of all kinds.  He explains the relevant technology in section 2 of his report.  After saying that electronic thermometers can take several forms, but are essentially instruments which use electronics to indicate temperature, and referring to a diagram which showed the main components of an infrared radiation thermometer, he continued as follows:
“2.10 … Heat energy from the target is focussed via the lens onto the heat sensitive detector. The field of view enlarges as the distance between the camera and the target increases.  Thus the further the distance between the thermometer and the target the larger will be the size of the target.  The output of the array is fed into an amplifier system.  The output can be used to detect heat, measure temperature, to monitor temperature (over a period of time) or as part of a temperature control system.
2.11 The Flir images are really an extension of this principle with the single detector replaced by a two-dimensional detector array.  This allows a thermal “image” to be produced.
2.12 All of the Flir products are infrared imagers which have the ability to display the temperature [with one exception which was not in dispute]. All are based on similar technology.
2.13 All of the imagers work in a non-contact mode. Essentially, the instruments work in a similar manner to a digital camera in the sense that there is a lens system which focuses the image on to an energy sensitive array.  However, in a digital camera it is light which is being focused onto a light sensitive array whereas in the Flir cameras it is radiated energy in the form of heat which is being focused onto a heat sensitive array.
2.14 The image produced by a digital camera is an image, which can be in colour or black and white, which represents the view of the subject scene when the photograph was taken. By comparison, the image produced by the Flir imagers is a thermal image of the subject scene.  The image has to be generated from the temperature data obtained from the sensor array. [He then explains how a range of colours is used to represent different temperatures]. The end result is usually an image where the colour tones can have some similarities with a light image.  For example, the image formed by heat radiated by a person will be in the general form of that person’s body and can be recognised as such by a person viewing the thermal image.
…
2.16 All objects which are at a temperature above absolute zero (-273ºC) radiate energy in the infrared spectrum.  The amount of heat radiated will be in proportion to the absolute temperature (-273ºC).  There is a small adjustment necessary depending on the material and the colour.  A black body will radiate the most heat.  The Flir imagers (as do other makes of imaging cameras) have an in-built offset capability to take account of this.  This is called the emissivity.
2.17 All of the Flir imagers are powered by battery which is contained in the handgrip. The batteries can be charged in the camera or removed and charged externally.
2.18 Each of the Flir imagers has the ability to store a number of images which have been taken (like a photograph except that it is a thermal image). Each image will have a colour scale representing temperature.  The high and low points of each image will depend on the range of temperatures in the image. Thus, when comparing images it is important to remember that a particular colour does not necessarily represent the same temperature.
2.19 Each imager, [with the one exception which was not in dispute], has the capability to make a temperature measurement which is then displayed on the LCD display.  The temperature measurement is based on a small area in the centre of the image and is the average temperature of the pixels contained in that area.
2.20 The imager cannot take normal pictures.  It can only take infrared pictures.”
18.	Both witnesses were cross-examined by counsel, and answered questions put to them by the members of the Tribunal.
19.	On the basis of the written and oral evidence before them, the Tribunal made findings of fact which are set out in paragraph 5 of the Decision. It will be sufficient to quote their primary findings of fact contained in sub-paragraphs (1) to (5), none of which are in dispute:
“(1) [Flir] is a Swedish company which manufactures thermal imaging digital cameras (although the expression camera was objected to by Mr Clues as it did not use visible light).
(2) BTIs were requested for four products (“the Products”), all of which have the following features: a lens that can be focused, a LCD display, a memory storage device, a detector (a microbolometer i.e. an array of pixels made from vanadium oxide), processing electronics, control software.  In each case the heated radiations are focused by the lens onto the microbolometer the resistance of which changes with the level of radiation falling on different parts of it.  By means of software these are converted into images with different temperatures displayed in colour, from a range of temperatures that can be selected from the maximum range, so that for example if the model measures temperatures between -40º to 120ºC the range can be set to a minimum span of 4ºC, say from 20º to 24ºC.  On the right of the image is a vertical scale showing the temperature at the top and the bottom of the chosen range of temperatures and the range of colours going from top to bottom.  The image is stored in JPEG format.  It is possible to turn off the vertical scale via a menu in which case there is a larger picture.  They can take spot readings of the temperature at the cross hair in the display. In order to obtain a more accurate temperature reading it is possible to set the emissivity factor (the amount of radiation from the body in question compared to a blackbody) according to the type of material being measured and its reflectivity.  An annual calibration is recommended by [Flir] to ensure accuracy of temperature measurement.  They come with a detailed user’s manual running to between 90 and 176 pages depending on the model.
(3) The four Products are:
(a) InfraCAM thermal imager (costing £3,000 to £4,000) [technical details are then given.] It is primarily used for preventative maintenance and building construction.
(b) ThermaCAM E45 infrared camera (costing £6,900). [Technical details are then given.] It is used for larger scale preventative maintenance work than the InfraCAM.
(c) ThermaCAM B2 infrared camera (costing £6,900). [Technical details are then given.] It is used mainly in the construction industry.
(d) ThermaCAM P25 infrared camera (costing £17,650). [Technical details are then given.] It is mainly used by certified thermographers in conjunction with analytical software packages such as Reporter (costing £3,000) for surveys for large companies of their plant, the maintenance of a factory, preventative maintenance in the oil and steel industries.
(4) [Flir] makes another product, Thermovision Scout (costing £6,500), which works on the same principle but without the temperature scale on the right of the image and without the ability to measure spot temperatures, and which cannot be calibrated.  This fits the description in the CNEN to heading 8525 and is so classified, and this is not in dispute.
(5) 50% of the market is for condition monitoring particularly in factories; 25% in the building industry to detect defective construction or insulation, and leaks; and 25% for automation, scientific and miscellaneous uses.”
20.	The documentary material before the Tribunal included sales and promotional material for the four products, and the user’s manual referred to in the Decision.  This material shows, as one would expect, that the products were sold and marketed as devices which would provide thermal images, which could be used for a variety of purposes.  They were not sold as thermometers, although the ability to measure and display temperatures was an important part of the function of these products (unlike the Thermovision Scout, which lacked the ability to measure spot temperatures and could not be calibrated).
The decision of the Tribunal
21.	After recording the submissions on each side, and the relevant principles of law (as to which there was little, if any, dispute between the parties), the Tribunal began their consideration of the question by setting out their understanding of the objective characteristics of the Products:
“10. We start by setting out our understanding of the objective characteristics of the Products which is that in part they are akin to digital cameras, and in part to electronic thermometers, both operating by using infra-red radiation.  Each [function] exists separately.  [Flir’s] Thermovision Scout is an example of the former [function] which shows only an image without any temperature and is mainly used by the police for detecting people in the dark.  Infra-red spot thermometers also exist as separate instruments costing amounts in the hundreds of pounds as opposed to the Products costing from £3,000 upwards.  A user would want to use both characteristics at least sometimes otherwise there would be no point in buying the Products since a cheaper alternative with one function would be available.  While there are some uses, such as showing where there is heat loss from a building, where the precise temperature is not required, this may still be required in a report to show the difference in temperature.  In other circumstances, such as where one electric cable was hotter than another, the measurement of the temperature of each would be necessary to see which was outside the normal temperature range.”
(In the above quotation, I have taken the liberty of inserting a comma after the word “thermometers” in the first sentence, and the word “function” in two places, in order to assist in bringing out the essential point which the Tribunal are in my judgment making. Viewed objectively, each of the products has two functions or capabilities: an imaging function, and the ability to measure temperature.  Although users will sometimes require one function rather than the other, they would not buy the product unless there were likely to be times when they would require both functions, because if that were not the case cheaper alternatives would be available.)
22.	The Tribunal then proceeded to ask themselves whether the products fell within the three headings contended for by the parties.  They started with heading 8525 (digital cameras). They held (in short) that the products would indeed fall under heading 8525, were it not for the CNEN to heading 8525 which implicitly excludes from the heading thermal-imaging cameras which have the ability to measure temperatures or represent the measured temperature values in figures.  The CNEN was not, in itself, legally binding, but it did not contradict the heading, and in those circumstances the jurisprudence of the ECJ indicated that it should be followed: see in particular Case C-400/05 BAS Trucks BV v Staatssecretaris van Financien, [2007] ECR I-311, at paragraph 40, and Case C-405/95 Bioforce GmbH v Oberfinanzdirektion Munchen, [1997] ECR I-2581, at paragraph 11.  It is unnecessary for me to spend any longer on this aspect of the case, because it is now accepted by Flir that the Tribunal was correct to follow the CNEN and to decide that the products in question do not fall under heading 8525.  Accordingly, the only contest on the appeal to this court has been between headings 9025 (thermometers) and 9027 (instruments for measuring or checking quantities of heat).
23.	There is no dispute that the products fall under heading 9025 as thermometers, and the Tribunal so held in paragraph 11(2) of the Decision. As they rightly said, each of the products could measure temperature both on the scale at the right-hand side of the image and by means of the spot readings.  
24.	The Tribunal found the question whether the products also fell under heading 9027 more difficult, but decided that they did, essentially on the ground that in lay terms the products do measure or check quantities of heat, albeit in strictly scientific terms a measurement of temperature is not a measurement of quantities of heat.  They expressed their reasoning in paragraph 11(3) of the Decision as follows:
“We find the question whether the Products are “instruments and apparatus for measuring or checking quantities of heat” more difficult.  This refers to quantities of heat, sound or light.  As a scientific matter we would follow Mr Clues’ evidence that the “quantity of heat” is a measure of energy and is measured in calories or joules; the Products do not measure this, as a calorimeter does.  Measuring a quantity of heat would imply measuring the resulting change in temperature, rather than temperature itself.  The quantity of sound could be the frequency (pitch) or the loudness, which corresponds to the brightness of light.  The quantity of light is strictly the rate of flow of light from a source but exposure meters are listed in the heading (and photometers and luxmeters are mentioned in the HSEN), which measure the intensity of light, which must therefore qualify as a quantity of light.  The actual readings of the values for heat, light and sound are delivered in modern instruments from a measurement of radiation of energy which is converted by the instrument into an absolute value in its read-out in the same way as the Products.  We are not therefore convinced that we should follow scientific precision here any more than being concerned whether an instrument recording an infra-red radiation picture is a camera.”
[They then referred to an earlier Tribunal decision in which the concept of “measuring and checking” had been elucidated, in relation to measuring and checking electrical quantities in heading 9030, as involving the determination of quantity expressed as a figure (measuring) and something which gives either a  yes or no result, such as whether current is passing (checking)].
“The Products express as a figure a quantity of heat in the non-scientifically strict sense of the amount of radiation from the target expressed as a temperature, which is analogous to what an exposure meter does. We also consider that they do check a quantity of heat in the sense of whether heat is being radiated or not, and by setting the span, whether the temperature is above or below a set figure or within a range as small as 4ºC. Accordingly the Products also fall within this heading.”
25.	Having held that the products could in principle be classified under either of the relevant headings, the Tribunal then had to choose between them.  For this purpose they had to apply in turn the rules contained in GIR rule 3.  They considered that rule 3(a) was not applicable, because neither heading provided the more specific description: the products were in part thermometers, and in part instruments for checking quantities of heat, and neither function was more specific than the other.  They also considered that the answer could not be found in rule 3(b), because that rule applies only to mixtures or composite goods which can be divided into separate physical components, and it cannot be used to resolve differences which are merely functional: see the judgment of the Court of First Instance in Case T-243/01 Sony Computer Entertainment Europe Ltd v Commission of the European Communities, [2003] ECR II-4189, at paragraphs 119 to 128. Accordingly, the Tribunal were left with the “tie-break” provision in rule 3(c), which categorised the products under the later of the two headings in numerical order, that is to say under heading 9027.
Discussion
26.	Counsel for HMRC advanced his case in a number of ways, but his fundamental point was that the Tribunal erred in law in holding that the products were capable of falling within heading 9027.  He argued that it is apparent from the terms of the headings themselves that a distinction must be drawn between instruments known as thermometers, which measure temperature, and instruments which measure or detect quantities of heat. The scientific distinction between heat and temperature was made clear by Mr Clues, both in his report and in his oral evidence.  Temperature is measured by reference to an absolute standard, and is calibrated by reference to the degree of difference from absolute zero.  Heat, by contrast, is the amount of energy required to move the temperature of a given object from one point to a higher point. It is measured in calories or joules, and according to the uncontradicted evidence of Mr Clues the quantity of heat would be defined by the formula “mass x specific heat x change in temperature”.  An instrument which measures heat in this scientific sense is a calorimeter, not a thermometer. It is true that the products in question operate by detecting infrared radiation, which may properly be called “heat energy”, but they do so in order to measure temperature, not to measure heat.  
27.	The effect of the Tribunal’s decision, argued Mr Beal, will be to treat all thermometers (regardless of whether they are electronic or not) as instruments that measure heat, and thus in effect to subsume the relevant part of heading 9025 under heading 9027.  Furthermore, it is clear from the terms of the CN itself, and the accompanying HSENs, that the instruments covered by Chapter 90 are widely used for scientific purposes.  They are instruments which are used to perform accurate measurements, for a wide variety of purposes.  A corresponding degree of precision and scientific literacy should therefore be employed in interpreting the terminology of the headings.  The Tribunal had erred in adopting a layman’s, non-technical approach to the interpretation of language that was essentially technical and scientific in nature, and they had done so in a way that contradicted the only expert evidence before them.
28.	These submissions were attractively and persuasively advanced by Mr Beal, but in the end I find myself unable to accept them.  I was shown no authority which supports the proposition that the language of the relevant headings should be interpreted with scientific precision, and it seems to me inherently improbable that such an approach should have been intended for a tariff code which has to be applied by businessmen and customs authorities worldwide.  The appropriate linguistic register is in my view that of the intelligent businessman, not that of a GCSE physics student.  In ordinary parlance, the concepts of heat and temperature are often used interchangeably, and it is perfectly natural to describe a thermometer as an instrument which measures heat.  
29.	It is relevant to note in this connection, as counsel for Flir pointed out, that the HSEN for heading 9027 says in terms that the heading excludes:
“(h) Hydrometers, thermometers, hygrometers and similar instruments of heading 9025, whether or not for use in laboratories.”
There would be no need for this clarification if thermometers were, by their very nature, incapable of falling within heading 9027 as instruments or apparatus for measuring or checking quantities of heat.  This exclusion also seems to me to answer Mr Beal’s point that the headings should not be interpreted in a way which leads to thermometers coming under both headings. In principle, thermometers could indeed find a home under either heading, but heading 9025 is clearly the more appropriate one, both because it is more specific (it refers to thermometers in terms), and because of the guidance given in the HSEN for heading 9027.
30.	This brings me on to the next point, which is that nobody as a matter of ordinary usage would describe the products in the present case as thermometers.  They are, rather, thermal imagers.  The infrared radiation emitted by the target objects, in the form of heat, is detected by the imagers and translated into a visual image.  That is a core function of the products, and although they also measure temperature, nobody would buy a thermal imager if a thermometer was all that they required.  I agree with counsel for Flir that to describe the products solely as thermometers would be inapt and reductive.  That, in turn, suggests that heading 9025 is by no means self-evidently the only appropriate category within which to place them.
31.	Furthermore, even on a strictly scientific approach, it is undeniable that the imagers operate by detecting heat in the form of infrared radiation.  As Mr Clues says in paragraph 2.13 of his report, it is radiated energy in the form of heat which is focused onto a heat sensitive array.  Because the amount of heat radiated by a body depends on its temperature, the pattern of heat radiation detected by the instrument can be transformed into a visual image, with a range of different colours being used to show the relative temperatures of the target surfaces. This basic function is performed even if the temperature scale is switched off, and for many purposes the user will not need to know the actual temperatures involved.  To describe this process as the measurement or checking of quantities of heat may not be strictly accurate in scientific terms, but it seems to me a perfectly reasonable layman’s description of an instrument which uses heat emissions to measure relative temperatures.  The Tribunal saw an analogy to this in what an exposure meter does, the point being that exposure meters are expressly referred to in the relevant limb of heading 9027 and must therefore be regarded as (or at least akin to) instruments which measure quantities of light. The Tribunal may well be correct about this, but the expert evidence before them did not deal with corresponding issues relating to the measurement or checking of quantities of sound or light, and neither side has sought to rely upon any such analogy, at any rate on the appeal to this court.  I therefore prefer to say nothing about the strength or otherwise of the analogy, and confine myself to saying that I agree with the Tribunal that the products do indeed fall within heading 9027 as instruments which measure quantities of heat in a relatively non-technical sense.
32.	 I also agree with the Tribunal that the products may reasonably be regarded as instruments which check a quantity of heat, because they detect whether or not heat is being radiated by the target surfaces, and the temperature controls can be set to operate within specified limits down to a range as small as 4ºC. The concept of checking, as opposed to measuring, quantities of heat, is not (so far as I am aware) one that has any precise scientific connotation, and its inclusion in this part of heading 9027 seems to me a further indication that scientific precision is not, here at least, of paramount importance.  After all, if the intention had been to restrict the scope of this part of the heading to calorimeters, or similar instruments, they could have been referred to by name, just as many types of scientific instruments are expressly referred to elsewhere in the heading. 
33.	Once the conclusion has been reached that the products fall within both headings, the rest in my judgment follows without difficulty.  Neither heading can be regarded as providing the more specific description, because the two functions identified by the Tribunal are of equal importance, and it would in my view be a travesty of the facts to say that the products operate mainly, or predominantly, as thermometers.  As the Tribunal say in paragraph 13 of the Decision, “neither is the more specific description: they are in part thermometers and in part instruments for checking quantities of heat, and neither is more specific”.  It is common ground that, if GIR 3(a) does not apply, rule 3(b) cannot be used to resolve differences in function.  Accordingly, recourse must be had to rule 3(c), which is admittedly arbitrary in its operation, but does at least provide an answer to the question.
34.	This is not a conclusion which I reach with any feeling of intellectual satisfaction, because rule 3(c) is by its nature a rule of last resort, and there is no particular logic in the numbering of the headings which might be supposed to make a later number more appropriate than an earlier one.  However, there is a paramount need for certainty, and the avoidance where possible of time-consuming and expensive disputes.  Rule 3(c) does at least have the merit of being clear and simple to apply, even though I feel an instinctive reluctance to have recourse to it.  My reluctance is tempered, however, by the absence of any indication in the jurisprudence of the ECJ that recourse to it should if possible be avoided.
35.	Mr Beal took a number of other points, both in his oral and in his written submissions, but they all seemed to me to be subsidiary to his main argument that the products are incapable of falling under heading 9027.  With no disrespect to him, I will therefore deal with them more briefly.
36.	He argued that the Tribunal failed to give due regard to the exclusionary note to the HSEN accompanying heading 9027, which as I have already said makes it clear that thermometers are to be categorised under heading 9025.  It is true that the Tribunal did not refer to this HSEN, but it seems to me that, if anything, it helps Flir.  It presupposes that thermometers may, in principle, fall within both headings, and resolves any doubt on the question by directing that heading 9025 is to prevail.  However, this guidance only applies in relation to thermometers properly so-called, and for the reasons which I have already given it is clear that the products were much more than mere thermometers. They are thermal imagers.  I therefore agree with counsel for Flir that the exclusion of simple thermometers does not assist in their classification. 
37.	Mr Beal also placed some reliance on the history which led to the adoption on 30 April 2003 of the CNEN to heading 8525, and the subsequent issue by the German authorities in 2006 of BTIs in respect of thermal imagers that could measure and display temperature classifying them under heading 9025.  This history is summarised by the Tribunal in subparagraphs 5(7) and (8) of the Decision.  However, the only relevance of the CNEN to heading 8525, for present purposes, is that it explains why the products in issue (unlike the Thermovision Scout) cannot be classified as digital cameras. That proposition is no longer in dispute.  The BTIs issued by the German authorities take matters no further, because the question of classification under heading 9027 was not considered by them, and the only contest was between headings 8525 and 9025.  In any event, BTIs issued by other customs authorities are not in any sense legally binding, and at the highest they can have only persuasive value.  For good measure, counsel for Flir was able to show me (as she had shown the Tribunal) certain BTIs issued by the authorities in India and the USA which classify thermal imaging products with a temperature measuring capability under heading 9027.
38.	Mr Beal also criticised the Tribunal for failing to consider whether a reference to the ECJ would be appropriate.  However, I agree with counsel for Flir that there was no need for the Tribunal to make a reference.  The need for restraint by national courts in making references to the ECJ in cases concerned with the customs classification of goods was emphasised by Advocate General Jacobs in Case C-338/95 Wiener SI GmbH v Hauptzollamt Emmerich, [1997] ECR I-6495: see in particular paragraphs 20 and 38 of his opinion.  The Tribunal evidently took the view that no general point of principle arose which required them to make a reference at this stage, and sitting in a court from which a further appeal is possible I would take the same view myself.
39.	Finally, Mr Beal submitted that the Tribunal’s decision on the facts displayed an error of law in the Edwards v Bairstow sense. However, this submission amounted to no more than saying that the Tribunal should have followed Mr Clues’ expert evidence on what is meant, in scientific terms, by “measuring quantities of heat”. If, as I think, the Tribunal were correct to hold that the wording of heading 9027 does not have to be interpreted in a strictly scientific manner, this objection has no substance.  If, on the other hand, the Tribunal were wrong on this point, they erred in law in their interpretation of the heading itself, and it is unnecessary to attack their findings of fact.  In any event, they clearly accepted Mr Clues’ evidence as being scientifically correct: see in particular paragraph 11(3) of the Decision. The real dispute between the parties is about the interpretation of heading 9027, not about the findings of fact made by the Tribunal.
40.	I must deal finally with a point which I raised myself during the course of the hearing, and on which the parties helpfully supplied me with further written submissions after I had reserved judgment.  The particular subheading of heading 9027 within which Flir says the products should be placed is subheading 9027 50 00, “Other instruments and apparatus using optical radiations (UV, visible, IR)”. The point which concerned me was whether the products could properly be described as ones which used “optical” radiations, given that they operate by detecting emissions of heat radiation.  On reflection, and with the assistance of the further submissions from the parties, I am satisfied that there is nothing in the point.  The short answer, as counsel for Flir rightly submits, is that the wording of the subheading provides its own dictionary, and makes it clear that both ultraviolet and infrared radiations, as well as visible light, are to be regarded as optical radiations for the purposes of this definition. The heat radiation which is detected by the products all falls within the infrared part of the electromagnetic spectrum, and is therefore covered by the definition.
41.	Descriptions in simple terms of the electromagnetic spectrum can, of course, be found in dictionaries, textbooks and encyclopaedias, but I will cite a short extract from the user’s manual for the ThermaCAM P25 because it formed part of the evidence before the Tribunal:
“The electromagnetic spectrum is divided arbitrarily into a number of wavelength regions, called bands, distinguished by the methods used to produce and detect the radiation.  There is no fundamental difference between radiation in the different bands of the electromagnetic spectrum. They are all governed by the same laws and the only differences are those due to differences in wavelength.”
The spectrum is divided into six main bands, namely (in ascending order of wavelength) x-ray, ultraviolet, visible, infrared, microwaves and radiowaves. Thermography makes use of the infrared spectral band.
42.	Accordingly, although at first sight it may seem odd, at any rate to a layman, to describe heat radiation as optical radiation, I am satisfied that the definition is simply concerned with radiation which falls within the ultraviolet, visible and infrared bands of the electromagnetic spectrum.  The concept of optical radiation is not necessarily confined to visible light.  Nor does the definition draw any distinction between heat and light.  I agree with counsel for Flir that it covers any form of electromagnetic radiation falling (relevantly) within the infrared band of the spectrum.
43.	This interpretation needs no external support, because (as I have said) the wording of the subheading provides its own dictionary. However, it is worth noting, as counsel for Flir helpfully pointed out, that the phrase “optical radiations” is defined in Council Directive 2006/25/EC (which lays down minimum health and safety requirements regarding the exposure of workers to risks arising from artificial optical radiation) as encompassing “any electromagnetic radiation in the wavelength range between 100nm and 1mm”. That range of wavelengths spans the ultraviolet, visible and infrared radiation bands.  Counsel did not suggest that the directive should be used as a direct aid to construction of heading 9027, because there is ECJ authority which indicates that the terms of the CN are autonomous, and are not to be determined by reference to other Community legislation: see in particular Case C-405/95 Bioforce GmbH v Oberfinanzdirektion Munchen, [1997] ECR I-2581, at paragraph 11. However, the definition in the Directive is of some assistance, in my judgment, because it shows that the term “optical radiation” may properly be used to encompass at least radiation falling within the ultraviolet and infrared bands of the spectrum.
Conclusion
44.	For these reasons I consider that the Tribunal came to the correct conclusion and this appeal must be dismissed.