England and Wales Court of Appeal (Civil Division) Decisions

Maccaferri Ltd. v Hesco Bastion Ltd. [2002] EWCA Civ 264 (7th March, 2002)

IN THE SUPREME COURT OF JUDICATURE
COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE PATENTS COUNTY COURT

		Royal Courts of Justice Strand, London, WC2A 2LL
		07 March 2002

Lord Justice Auld:

1. This is an appeal by Maccaferri Limited (“Maccaferri”) against the findings of H.H. Judge Ford in the Patents County Court on 27^th April 2000 that claim 1 of the patent of Hesco Bastion Limited (“Hesco Bastion”) of a wire mesh cage for use in building or engineering works – a “gabion” – was valid and that Maccaferri had infringed it.
2. The issues on the appeal are: first, whether, on a proper construction of claim 1 of the patent, Maccaferri has infringed it by importing into, and selling in, the United Kingdom a wire mesh cage structure called “Flex-Mac”; and, second, if the claim is construed in a manner that encompasses the Flex-Mac structure, whether the claim is invalid by reason of obviousness in the light of the prior art disclosed in Czinki (EP O 202 552). On the issue of infringement, Mr. Simon Thorley, QC, for Maccaferri, urged a narrow construction. On the issue of validity, if it arose, he argued for a broad construction.
3. A gabion in its most general form is a cage-like structure constructed of a mesh type material transported to and, to the extent necessitated by its design, erected on site for filling with material to provide a solid structure for engineering or fortification purposes. In the 17^th and 18^th centuries it took the form of wicker baskets filled with earth and stones mostly as a protection for artillery emplacements and other military positions. Its prime function now is in the provision of wire mesh cages for filling with rocks and other material as a solid foundation for building and engineering projects such as sea defences and shoring up landscaping embankments.
4. Hesco Bastion’s patent is European Patent (UK) No. 0 466 726 B1 applied for in April 1990 and granted in November 1995. It is entitled “Improvements Relating To Building And Shoring Blocks” and relates to a wire mesh structure that can be delivered to site in a folded form and there readily unfolded to form a series of connected cavities into which stones, sand or other building or engineering materials can be packed.
5. Maccaferri’s allegedly infringing product, Flex-Mac, also consists of a wire mesh structure capable of delivery to site and unfoldable there for similar use to that of Hesco Bastion’s product.
6. Claim 1 of the patent is for a cage structure consisting of several cavities and having two “side walls” and two “end walls”. In between the end walls there are a number of “partition panels” separating the cavities one from another. The side walls are made up of a plurality of panels. I set out claim 1 in its own words but divided, as Mr. Thorley has helpfully suggested, into ten essentials:

“1. A cage structure

2. which is for use at a site where the structure will be filled with sand, soil and other building material

3. wherein the cage structure is made up of pivotally interconnected open mesh work panels

4. which are connected together under factory conditions so that the cage can take a flattened form for transport to site

5. where it can be erected to take a form in which panels thereof define side and end walls and an open top through which the cage structure can be filled

6. and under said factory conditions said panels defining the cage side and end walls

a. are pivotally interconnected edge to edge and

b. are relatively foldable to lie face to face in the flattened form for transportation to site, and

c. can be relatively unfolded to bring the cage to the erected condition without the requirement for any further interconnection of the side and end walls on site,

characterised in that

7. the side walls each comprise a plurality of side panels

a. pivotally connected edge to edge and

b. folded concertina fashion one relative to another,

8. and the side walls are connected by partition panels which are pivotally connected thereto,

9. the cage structure being adapted to be erected on site by pulling it apart by the end walls

10. and when it is moved from the flattened form to the erected condition the side panels unfold and define with the end walls and partition panels an elongated wall structure having a row of cavities to be filled with said building material and of which each partition panel is common to the pair of cavities adjacent the partition panel.”

7. There are a number of aspects of gabion design for which the established art at the time of the patent already provided. These included convenience of transport to site in folded flat pack form and part construction on site by folding or bending into position and connecting panels one to another with clips or other mechanical devices. The 1960 Penfold patent (UK Patent No. 845 863) is an example of such a gabion. An important feature of the Hesco-Bastion patent is that the mere unfolding of the structure without need for further bending, folding or fixing on site, enables more speedy erection and filling on site, particularly important, for example, where the gabion is intended for resistance to tidal or wave action or for military purposes.
8. The patent specification describes the invention in a form mirroring claim 1, identifying a number of advantages of the invention over the prior art disclosed in the Penfold patent. Though expressed in various ways, the claimed advantages of the Hesco Bastion patent over the prior art can be condensed into one, namely the facility of rapid erection, simply by unfolding, on site. The cavities thus created are then immediately available for filling, usually mechanically. The cavities are polygonal. They may be hexagonal, as in the specific embodiment depicted in the specification of the patent, but the claim is not so limited and, say Hesco Bastion, may extend to square or rectangular or other polygonal shapes.

Construction

9. First, it is necessary to construe the patent and the claim since, as Aldous LJ pointed out in Wheatley (Davina) v. Drillsafe [2001] RPC 133, 141, CA, the extent of the protection provided by a patent is of importance on the issues of both infringement and validity. Maccaferri’s case is that the inventive concept embodied in the patent (and which achieves the stated objectives) is for a pre-fabricated cage structure folded like a concertina so as to be opened simply by pulling one end away from the other to produce a row of cavities. It places emphasis on the word “concertina” in essential 7(b) of the claim, which refers to the plurality of side panels being “folded concertina fashion one relative to another”, and on essentials 9 and 10 describing ready erection of the structure by pulling one end of it away from the other to open the cavities ready for filling. Hesco Bastion’s case is that the essence of the invention over the previous Penfold art lies not in the precise manner of its unfolding, but in its facility for quick erection on site by unfolding and opening out on site an already connected structure, instead of requiring part construction and connection on site by folding or bending into position and fixing clips or other mechanical devices.
10. The main evidence before the Judge was of the expert witnesses for each party. Hesco Bastion’s expert was Mr. David Jones, a chartered civil engineer with experience of design and construction of gabion installations, particularly in relation to marine and river works, but not of the design or manufacture of cage structures themselves. Maccaferri’s expert was Mr. Graham Marshall who, save for a few years in the early 1980s, had worked for Maccaferri for some 25 years. At the time of giving evidence, he was the head of Maccaferri’s South East Asian operations. The Judge, while noting the duality of his role as an expert and an employee of Maccaferri, said that his contribution on many issues was useful and objective.
11. The Judge held that the claim should be given a broad construction by reference to its facility for speedy erection on site by unfolding and opening and without the need for further fixing. He said that neither the claim nor the specification warranted a more restricted meaning by reference to the shape of the cavities when the structure is unfolded and opened, or to the precise manner of its unfolding and opening, or as to whether some further opening movement was required after unfolding. He said:

“2.6 Counsel for Maccaferri has sought to argue that the claim excludes square and rectangular cavity construction because, he says, the side walls of each cavity must have a plurality of side panels. Not so. The described and illustrated specific embodiment does have hexagonal cavities but it is illustrative, not limiting. The language of the specification is quite clear. In column 1 line 58 and in Claim 1 there is express reference to cage side walls. It is the cage sidewalls that each comprise a plurality of side panels.

2.7 Most of the debate between the parties on the construction (interpretation) of the claim concerns the folding and unfolding of the pivotally connected panels. The panels defining the cage side and end walls are relatively foldable to lie face to face in the flattened form. The panels that define the side walls are folded concertina fashion one relative to another. … panels can be face to face even when there may be something between them, the purpose of the exercise being to pack the panels flat. As to … ‘folding concertina fashion’ [it] makes use of what the dictionaries show to be a common expression, using the intransitive verb ‘to concertina”. However, definitions which focus on the idea of either irreversible collapse or of bellows-like compression and rarefaction of air are no help in the present context. More apt are the notion of a folding structure such as a concertina door, mentioned by Counsel for Hesco Bastion, and one definition in Webster’s Dictionary: ‘employing a hinged usually folding mechanism to make enlargement possible’. There is intended to be indicated a sort of zigzag fold which will be unfolded by pulling on the end walls. The skilled reader of the specification would realise that there may be, as has been demonstrated with models, more than one way of folding to achieve the desired result. It is not suggested that devising a folding sequence would cause the skilled person any difficulty.”

2.8 Erection on site by pulling the folded cage structure apart by the end walls causes the side panels to unfold and define with the end walls and the partition panels the elongated wall structure. It is disputed whether the claim covers a structure which has to be fully opened up by an additional movement of the stretched out structure. For Maccaferri it is contended that a single step fully opening process is required by the claim. For Hesco Bastion it is urged that nothing in the claim stipulates that the only step to be taken is pulling the ends apart. On balance, the latter view appears to be right. ‘Adapted to be erected on site by pulling it apart by the end walls’ and ‘when it is moved … to the erected condition the side panels unfold’ appear to express in broad terms the principle of operation rather than a precise sequence of steps which would exclude any additional ones. Column 2 line 48 of the specification is also broad. It says that the structure is created ‘by relative pivoting of the panels’ which is directly compared with the Penfold arrangement.”

12. Mr. Thorley said that the claim should be given a purposive construction, so taking into account the description and drawings in the specification, relying on section 125(1) and (3) of the 1977 Act and the Protocol on the Interpretation of Article 69 of the European Patent Convention. His main attack on the Judge’s reasoning was that he had given too broad a meaning to the concept of concertina folding by equating it in this context with a zigzag fold. He maintained that the specification made plain that the described speedy method of unfolding the structure was a crucial aspect of the invention, which met the objective of the patent in overcoming the disadvantages of the prior art. He referred to the passage in the specification, at col. 7, lines 18-20, “The cage structure according to the invention is simply erected at the site by relative pivoting of the panels” and the corresponding provision in essential 9 of the claim, of the “cage structure being adapted to be erected on site by pulling it apart by the end walls”. He said that the requirement of essential 7(b) of the claim that the side panels should fold “concertina fashion one relative to the other”, in addition to that of essential 6(a) and (b) that they should be pivotally interconnected and foldable so as to lie face to face, indicated something more than any “sort of zigzag” folding. He submitted that it meant “being folded like a concertina”, as depicted in the layered bellows structure in figure 1 of the specification illustrating the single pulling movement required to open the cavities ready for filling. He also maintained that it was an essential feature of such a concertina mechanism that the side of each cavity, not just of the whole of each cage side, should consist of more than one panel.
13. Finally, Mr. Thorley said that the word “concertina” had no special meaning in the context of gabions and should be given its natural meaning derived from Wheatstone’s patent for a musical concertina filed in 1844 (No. 10,041) and to be found in dictionary definitions. He drew attention, in support of this argument, to Mr. Jones’, Hesco Bastion’s expert’s, description of the concept:

“pivotally connecting the individual cages or cells as described in the Patent specification so that they form a long line of connected hexagonal cells, which furthermore can be packed flat by being concertina folded for transportation in such a manner that they can be erected by ‘pulling out and extending’ without the need for fixing any further anchors, hinges, stays, diaphragms etc.”

14. Mr. Mark Platts-Mills, QC, for Hesco Bastion, did not suggest that the words “folded concertina fashion” have a technical meaning in the art. He too said that they should be given their ordinary meaning which, he maintained, encompasses any broadly zigzag sort of folding. He relied on certain dictionary definitions and usages found in other contexts. In short, he said that it was plainly not the object of the invention to create something that looks like Mr. Wheatstone’s patented concertina of 1844, but simply a multi-cavity structure capable of being folded flat for ease of transport and ready erection on site by unfolding. He dismissed as misconceived Mr. Thorley’s suggestion that, as a matter of construction, the words “concertina fashion” must mean something more than the zigzag fashion of folding contemplated by the other essentials of the claim. First, he pointed out that it is not plain how the other essentials already provide for such a fold. The requirement in essential 6(b) that the cage side and end walls should be “relatively foldable to lie face to face in the flattened form” does not, he submitted, require a zigzag or any other particular type of fold. Second, he noted that, even if a requirement of zigzag folding could be drawn from that and/or other essentials, it would be wrong to apply a presumption against repetition so as find a different and more precise meaning for the essential, “folded concertina fashion”. He too relied on section 125(3) of the 1977 Act, in its reference to the Protocol, adding that a patent is not a statute and should not be construed as if it were.
15. As an aid to construction, section 125 is, and is the result of, a compromise. Section 125(1) provides that, unless the context otherwise requires, an invention is that specified in the claim of the specification of the patent, as interpreted by the description and any drawings contained in the specification, and that the extent of protection conferred shall be determined accordingly. But that seemingly straightforward guidance is glossed by section 125(3) by reference to the Protocol requiring courts to determine the extent of protection by taking a position between the extremes of literal interpretation of the wording of the claim and of treating it only as a guideline, so as to combine a fair protection for the patentee with a reasonable degree of certainty for third parties.
16. As Aldous LJ explained in Wheatley, at 141-2, the object of all that is to ascertain objectively the intention of the inventor: 1) by reading the claim in the light of the specification; 2) if it has an accepted meaning, as seen in its context through the eyes of a reader skilled in the art, here an engineer familiar with these cage-like structures; and 3) if it does not have an accepted meaning, by the court construing it in its context and putting itself, so far as it can, in the place of the skilled reader.
17. As an aid to that task where necessary, the Courts have devised a three step approach where the alleged infringement is not caught by the language of the claim but may nevertheless amount to a “variant” of it within the reasoning of the House of Lords in Catnic v. Hill & Smith [1982] RPC183, as explained by Hoffmann J, as he then was, in Improver v. Remington [1990] FSR 181, at 189. The steps are that the variant would only be caught by the claim if 1) it had no material effect upon the way the invention works; and 2) that immateriality would have been obvious at the date of publication of the patent to a reader skilled in the art; and 3) the skilled reader would not have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention. As Hoffmann J explained, the first two steps involve consideration of questions of fact, but the third is one of construction.
18. It is common ground, as I have said, that none of the words in the claim has a technical meaning. It is, therefore, necessary, to consider the words as a matter of ordinary English usage as they would be read, in the light of the description and drawings in the specification, by an engineer familiar with such cage-like structures. The patent, in its description of the invention, contrasts it with the prior art of Penfold in the speed and convenience of erection on site:

“The present invention seeks to provide a cage structure erectible on site to provide a structural block in a rapid and efficient manner”

19. This is carried through into the body of the specification and reflected in a number of the essentials of the claim, one of which is the “concertina” fashion of folding mentioned in essential 7. Like all the other words of the claim, the word “concertina” is not defined in the specification, nor has it any meaning in the trade. We have been referred to a number of dictionary definitions and usage in promotional literature for other quite different products, such as sliding doors, filter cartridges and window blinds, and for services such as book-binding. Although a concertina is a well-known musical instrument in the form a pair of bellows, usually hexagonal, it is plain both from dictionary definitions and common usage illustrated by such literature that, the word “concertina”, in its adjectival form, is often used to describe simple folding in zigzag fashion. Why it should have any more precise a meaning in this context it is hard to understand. There can be nothing relevant to the functioning of this invention in the precise manner of folding required for bellows. The nearest Mr. Thorley could get to insisting on that design is by reference to essentials 9 and 10 of the claim in their description of the manner of opening of the cavities as part of the process of unfolding. But there is nothing in the claim or the description in the specification to require the ends of the structure when being unfolded to remain parallel or in the same axis or that, once unfolded to its full extent, the cavities should automatically open without some further small movement of the frame. As Mr. Platts-Mills observed, it does not matter how the product is unfolded if, by the actions of unfolding, it can be readily erected on site without further fixing of the Penfold sort.
20. In my view, to focus, as Mr. Thorley did, on the word “concertina” so as to dominate or confine the claim in the way he suggested was to miss the essence of the invention and its advance over the prior Penfold art, namely the introduction of a factory made hinged construction that could be erected on site by unfolding it and without further fixing. I agree with the Judge that the draftsman’s use of the word in this adjectival sense does not indicate any more than a structure capable of being folded in a zigzag sort of way and does not and could not sensibly confine the claim to the hexagonal design which a concertina requires for wholly different reasons.
21. Nor is there anything else in the wording of the specification or the claim to require the cavities to have more than one side panel so as to be hexagonal when unfolding or when fully opened. All that is required is that they should be polygonal. The hexagonal structure illustrated in the description and drawings of the specification, but not so identified in the claim, is simply an example. The patent thus follows common practice in making an invention of which there is a specific embodiment, but in making a claim not limited to that specific embodiment.
22. Accordingly, I am of the view that the Judge correctly construed the claim in accordance with the specification of the patent, as interpreted by the description and drawings, seen in their context. In so doing, he has properly concerned himself with a comparison of the invention with the prior art and not with the alleged infringement by Maccaferri.

Infringement.

23. Mr. Thorley submitted that Maccaferri’s Flex-Mac structure does not infringe claim 1 of Hesco Bastion’s patent.
24. The Flex-Mac is a rectangular multi-cavity cage structure with side, end and partition panels, for use on site where it can be filled with building materials. The side wall of each cavity is made up of one side panel and each partition panel is common to two cavities. It is constructed of pivotally interconnected open wire mesh panels and transportable in folded and flattened form. The cage side and end panels are relatively foldable in zigzag or other fashion so as tolie against each other, but with partitions folded between them. On site the structure can be erected by unfolding so as to define side and end walls and an open top separated into a number of cavities, all without the need for further fixing. Like the Hesco Bastion product it may be unfolded by pulling it apart by the end walls, so unfolding the side panels. But when unfolded to its full length, it requires an additional skewing movement of the end walls to open the cavities.
25. Mr. Thorley submitted that the Flex-Mac structure does not have the features of the Hesco Bastion claim as properly construed in that it is geometrically different from it and works and is deployed in a different way. He said that there are three main differences between the two, all derived from the fact, as he contended, that the side panels of the Flex-Mac are not folded concertina fashion one relative to the other. The first is that each side of each cavity of the Hesco Bastion structure has two pivotally interconnected side panels, each also pivotally interconnected to one of the side panels of an adjacent cavity, whereas in the case of Flex-Mac, each side of each cavity consists of only one panel pivotally connected to adjacent side panels of adjacent cavities. The second difference, Mr. Thorley claimed, is that the panels defining the cage sides and end walls of the Hesco Bastion structure are relatively foldable face to face in the flattened form, whereas the Maccaferri panels, when folded, are not folded face to face against corresponding panels because each pair has another panel between them. The third difference is that the Hesco Bastion structure opens the cavities automatically as one end is pulled away from the other, whereas the Flex-Mac’s unfolding involves a two stage process namely the production of a closed linear structure and then skewing the end panels so that they are at right angles with the side panels to open all the cavities.
26. Mr. Platts-Mills, in keeping with his submission that “folded concertina fashion” should be interpreted in the broad everyday sense of a zigzag type of fold, argued that Maccaferri’s Flex-Mac structure infringes the Hesco Bastion claim.
27. As to the other differences between the two on which Mr Thorley relied, he said, first, that there was no difference as to the number of side panels provided for in claim 1 and in the Flex-Mac product since, as a matter of construction of the claim, it did not specify how many side panels each cavity should have.
28. Second, as to the suggested difference that the Flex-Mac side panels do not, when folded, lie “face to face” as provided for by essential 6(b) of the Hesco Bastion claim because there is another panel between them, he dismissed it as “a rather extreme argument” noting that Maccaferri had not pleaded it and its expert, Mr. Marshall, had not supported it. He said that, in any event, there is nothing in the words “face to face” to prohibit something being interposed between the folded panels, the clear purpose of the essential being to provide for a system of folding the cage structure so that it is flat for ease of transport.
29. Third, as to the suggested difference from the claim in the method of unfolding the Maccaferri structure, he submitted that it met essential 9 in that it could be readily unfolded and erected “by pulling it apart by the end walls”, the opening taking a “chevron” form as illustrated in figures 6 and 7 of Appendix 3 to Hesco Bastion’s statement of case. As to Maccaferri’s suggested distinguishing feature of its product’s method of unfolding and erection, that it required a final skewing action to open the cavities, he said that, even if such a slight additional action is required, it is immaterial. The requirement in the essential that the structure should be capable of being erected on site by pulling it apart by the end walls does not exclude structures that may require such an additional opening action as the final stage of unfolding. As he put it, “the requirement is a description, in broad terms, of how the thing is unfolded – … not a precise set of instructions for erection”, and its purpose would be plain to a skilled man as contrasting the invention with familiar gabions of the Penfold variety requiring erection by bending panels and clipping them together on site.
30. For the reasons I have given on the issue of construction, I agree with those submissions of Mr. Platts Mills and the Judge’s similar reasoning. However, before leaving the issue of infringement, I should deal with the issue if, contrary to my view, Maccaferri’s Flex-Mac is not caught by the strict language of the claim, it nevertheless involves a “variant” of it in the Improver or Protocol sense. As to the first two improver steps, the Judge rightly identified the only possible candidate for consideration under this head as the two-stage unfolding of the Flex-Mac, and held that it would have been such an immaterial variant that Maccaferri would still have infringed claim 1 of the Patent. Mr. Thorley criticised the Judge’s conclusion in this respect as contrary to the evidence. Having considered the evidence of both Mr. Marshall and Mr. Jones to which Mr Thorley drew our attention, it seems to me that the Judge has accepted the main thrust of Mr. Thorley’s contention that the Flex-Mac structure involved a two-stage process, but that the second stage, the final unfolding to create the cavities, was such a minimal addition that it did not amount to a material difference. In my view, he was entitled to reach that conclusion on the evidence before him - one of fact, as Hoffmann LJ said in Improver.
31. The Judge, in expressing his conclusion, clearly had in mind the relationship between essential 6(b), of the claim in its reference to folding “concertina fashion” and essentials 9 and 10 which are concerned with the opening mechanism. He said:

“It is alleged that when you pull out and then extend the FLEX-MAC structure it does not open. In order to open it out one must skew one side of the structure sideways relative to the other. This is said not to come within the language of the claim. This Court disagrees for reasons already given but assuming that is correct and one has to consider the “variant”, it seems that the variant would indeed have no material effect on the way the invention works and this would have been obvious to the skilled reader. There seems to be no reason why the reader should regard strict compliance with language of the claim as essential. An additional slewing or skewing action appears to be a purely trivial variant. It is an action which opens all the cavities simultaneously but requires no additional functional features of the structure or assembly steps or labour.”

32. As to the third Improver step, I agree with the Judge that the difference between the two structures in the mechanics of the opening of the cavities as the culmination of the unfolding action is of such a trivial nature that the skilled reader in the art would have so regarded it and would not have understood the adjectival use of the word “concertina” in the claim as an indication that folding so as to reproduce the characteristics of the musical instrument was an essential requirement of the invention. Nor can it matter for achieving the intended purpose of speedy unfolding and erection on site whether each cavity has one side panel or two hinged side panels, provided that the unfolding and opening mechanism meets the requirements of the claim, which the Flex-Mac structure does.
33. Accordingly, I would uphold the Judge’s finding that Maccaferri’s Flex-Mac infringes claim 1 of Hesco Bastion’s patent if it is valid.

Validity.

34. Section 3 of the 1977 Act provides that an invention involves an inventive step if it is not obvious to a person skilled in the art. Thus, as Aldous LJ said in Wheatley, at 141, a patent is invalid if the extent of its protection includes the prior art or something that is obvious having regard to the prior art. This issue of obviousness only arises if Hesco Bastion succeeds in its argument of infringement. Maccaferri maintains that the patent should be revoked by reason of invalidity, relying on what it maintains are erroneous findings of the Judge as to the common general knowledge and the prior art disclosed in Czinki. Mr. Thorley’s contention was that on any construction of the claim that caught Flex-Mac, the claim was obvious over Czinki. For this purpose Mr. Thorley contended, contrary to his argument on infringement and against the possibility of its failure, that the claim was wide.
35. Before the Judge and on this appeal the difference between the parties was as to the inventive concept. Maccaferri’s case was that it is essentially an “expandable cage structure” in which the cavities expand as the structure is pulled apart. Hesco Bastion maintained that the essence of the claim could not be described as “an expandable cage structure” because the inventive concept falls to be defined by reference to claim 1 which contains many more essential elements. By reference to the claim, it characterised the inventive concept as the creation on site of an array of two or more cavities merely by opening the structure. The Judge preferred Hesco Bastion’s narrower approach, observing that it was consistent with the approach of Aldous LJ in Texas Iron Works Inc.s Patent [2000] RPC 207, at 239, to identification of the inventive concept by reference to the detail of the specified claim of the patent.
36. The Judge correctly identified the four questions to be answered on this issue, taking them from Oliver LJ’s formulation in Windsurfing International Inc. v. Tabur Marine (Great Britain) Limited [1985] RPC 59, at 73, as slightly amended by Pumfrey J. in Horne Engineering Company Limited v. Reliance Water Controls Limited [2000] FSR 90, at 109-110 to make the formulation conform to the terminology of the 1977 Act. It reads:

“There are … four steps which require to be taken …. The first is to identify the inventive concept embodied in the patent in suit. Thereafter, the Court has to assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and to impute to him what was, at that date, common general knowledge in the art in question. The third step is to identify what, if any, differences exist between the matter [forming part of the state of the art] and the alleged invention. Finally, the Court has to ask itself whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention.“

37. As I have said, the Judge preferred Hesco Bastion’s approach to identification of the inventive concept by reference to the essential elements of claim. In doing so, he contrasted the rival contentions of counsel and said:

“3.6 … It is not ‘an expandable cage structure’ because that omits many essential elements set out in claim 1. That [i.e. Hesco Bastion’s] approach is right in this case and is consistent with the approach approved by the Court of Appeal in Texas Iron Works. It also means that the skilled person, whose common general knowledge includes prior constructions of the type illustrated by Penfold, will understand what the problem was.”

38. Mr. Thorley’s first main complaint under this head was the Judge’s identification of the inventive concept. He criticised him for rejecting Maccaferri’s broad definition of the claim as an “expandable cage structure” since, on the evidence, that was how its inventor had described it and Hesco Bastion’s expert, Mr. Jones had accepted such a description when put to him in cross-examination. And he criticised the Judge’s acceptance of Hesco Bastion’s definition since, he submitted, it left out essential aspects, such as the manner of folding, and thus did not adequately reflect the detail of the claim. Mr. Platts-Mills adhered to his submission to the Judge, namely that, by reference to the claim, the inventive concept consisted of the creation on site of an array of two or more cavities on site merely by opening the structure.
39. Mr. Thorley’s second main complaint was of the Judge’s treatment of the issues of common general knowledge and of the differences between the invention and the prior art. This is what the Judge said about the prior art:

“4.1 …. The evidence of the expert witnesses seems to indicate that the gabion art was “stable” and had been so for some 40 years (Penfold was 30 years old). Gabions were made either of twisted mesh wire netting or spot welded mesh, the latter being more robust but, being stiff, requiring pivots if the product was to be delivered to sit in a flattened form. Structures providing up to 4 cavities were known. Gabions were sold in stock lengths. Vertical joints were all made on site, the mesh being folded or bent into position, using clips, helical wire spirals and other devices for fixing.”

40. Mr. Thorley submitted that the Judge’s brief reference to prior gabion art in that passage was correct so far as it went, but did not do justice to the issues and evidence on common general knowledge. He maintained that if it was a finding of the relevant common general knowledge, it was inadequate because it did not identify the knowledge, namely that of a person skilled in the art, having read Czinki with interest, but without any inventive skill. Mr. Platts-Mills, on the other hand, contended that the passage was more than adequate, maintaining that the Judge was plainly referring to gabions of the type that had been common general knowledge for years, “monolithic” structures comprising bases, sides and lids, giving them rigidity and contributing to their structural strength.
41. As to the obviousness of the differences between the inventive concept and the common general knowledge as respectively identified by the Judge, Mr. Thorley maintained that the Judge approached the question in the abstract without considering whether the claim was obvious in the light of the common general knowledge he had identified. He relied on two main matters of common general knowledge, which he maintained were illustrated by the teaching in Czinki. Czinki disclosed a factory made rectangular single cell welded mesh structure, with no top or bottom. It has sides that are vertically connected at the factory by clamps or swivels so that they can be folded flat by moving one side relative to the other. It has horizontal bracing bars and corner struts which require insertion on site, but no diaphragm or partition panel. Mr Thorley contended that the Judge made a fundamental error in not comparing the breadth of the claim with the breadth of disclosure in Czinki which is not restricted to lightweight structures. The only difference between Czinki and the claim is that Czinki is a design for a single cavity whereas the claim requires two or more cavities.
42. The first matter of common general knowledge relied on by Mr Thorley was the feature in traditional gabions of the Penfold type that they had up to four cavities divided by diaphragms or partition panels to strengthen the structure. As to the single cavity Czinki structure, he submitted that it would have been obvious to a person skilled in the art in the light of that knowledge to produce multi-cavity versions of it, either by inserting partitions or by joining them together with pivots. So there was nothing new in the claim in providing for multiple cavity structures. Mr. Platts-Mills’ response was that there was nothing special about multiple cavities; they were simply a side effect of introducing reinforcing diaphragms or partition panels. However, he maintained that there was no evidence to support the suggestion that it was part of the skilled man’s stock in trade to make multiple cavity versions of a wholly differently constructed gabion, for example, by connecting a series of two or more by means of hinges to produce a less stable structure. To credit the skilled man with such a state of mind was, he submitted, an exercise in hindsight.
43. Second, Mr. Thorley suggested that welded mesh and the use of pivots to connect panels and to enable their folding for storage and/or transport in flat packs such as that specified in claim 1 was merely an alternative to the use of twisted mesh and folding of a single panel for like purposes. A joint which in twisted mesh took the form of a fold in the panel could be produced in welded mesh by means of two panels connected by pivots or hinges. Penfold had disclosed the concept of flat folding of partially fabricated gabions for storage or transport and Czinki showed how it could be done with hinged instead of folded panels. Mr. Platts-Mills acknowledged the reality of such alternatives in mechanical terms, but pointed out that bending or unbending of the former after transport to site requires substantially more work on site than the mere opening up of a hinged structure. He also drew attention to the fact that at the priority date, on the evidence, there were no hinged sided gabions in use and gabion brochures all specified and illustrated the Penfold type with rigid corners made up on site. He submitted that it did not follow that a skilled man would turn a twisted mesh cage into a welded mesh cage and substitute pivots or hinges in place of folds, and there was certainly no evidence at the priority date that such an alternative was a matter of common general knowledge.
44. The Judge held that Czinki did not make the Hesco Bastion claim obvious. In criticising the evidence of Maccaferri’s witness, Mr. Marshall, on this point as hindsight, he distinguished it from the claim on two main grounds: first, that it relates to structures primarily intended for use in noise reduction, landscaping and the like; and, second, that it was a single cavity structure:

“5.3. … Mr. Marshall, in his report, very reasonably acknowledges that Czinki is concerned more with a gabion wall structure … than with its constituent gabions. Again he says, with hindsight, that he believes that if he had been asked in 1989 to design a gabion structure which could be erected quickly Czinki would have given him the idea of making a multiple cell gabion in which the vertical edges of the sides and diaphragms were joined together and could be folded flat by moving one side relative to the other. Mr. Jones was cross-examined about the obviousness of making a double cell arrangement of Czinki by adding two short side panels and a long horizontal panel at the top … He agreed with suggestions put to him that that could be done. However, as Hesco Bastion point out, Czinki’s interest is in an essentially lightweight cage structure which should even have bracing elements inserted before it can be filled. In cross-examination Mr. Jones pointed out that bracing elements (tie bars) can easily get bent and then will distort the sides of the cell. Further, the primary intended use of Czinki is for noise reduction landscaping or containing compost. That is a long way from building and shoring blocks and why anyone should consider making Counsel’s suggested modifications without being prompted by knowledge of the Hesco Bastion patent specification is completely unclear. …”

45. Mr. Thorley submitted that the Judge, in that passage, failed properly to apply the fourth Windsurfing requirement because he did not compare the full breadth of the claim with the full breadth of Czinki, but only with a particular embodiment of Czinki. He maintained that the claim does not exclude either of those characteristics and that they are, in any event, irrelevant. He said that the first is not a distinguishing characteristic at all since noise reduction barriers or bunds can be as substantial as many civil engineering projects of a structural or supporting nature. As to the feature of joining two Czinki structures together, he said that the proper question is what a skilled man without knowledge of the claim would have done and that it would have been obvious to him that two Czinki structures could be joined together. And, as to the feature in Czinki of the insertion of a brace and corner struts after erection, he submits that, although such an addition is not mentioned in the Hesco Bastion patent, other items are, such as cord, and lining material, and that a skilled man would have been well aware of the possibility of adding bracing elements, where needed, before filling them on site.
46. Mr. Platts-Mills put at the centre of his submissions on this issue, as he had done on the issue of construction of the patent, that the major innovation of the Hesco-Bastion patent over the prior Penfold art of some thirty years’ standing was ready erection of a multi-cavity bastion on site. He maintained that, given the long-standing “monolithic” nature, and consequent strength and stability, of gabions, it was by no means an obvious step to move from such design to the relative instability of vertical pivots and hinges in the side panels. More obvious, he submitted, would have been to make bigger four sided gabions and insert diaphragms or partitions. He cautioned the court against hindsight in forming a view that a step giving effect to an idea was obvious and required no invention, citing Lord Russell in Non Drip Measure Co. Ltd. v. Strangers Ltd. (1943) 60 RPC 132, at 142, and Lord Diplock in Technograph Printed Circuits Ltd. v. Mills & Rockley (Electronics) Ltd [1972] RPC 346, at 362, HL.
47. There is an additional and unresolved question of fact about the Czinki invention the answer to which could affect its relevance to the issues of the obviousness of differences between the claim and the prior art. It appears from the application for the patent to relate to a very small wire mesh basket of about the size of a house brick for filling with soil and used as a small building block, that is to say, miniscule in comparison with the Hesco Bastion claim dimensions.  As Mr. Platts-Mills put it in argument, drawing on the evidence of both Mr. Jones and Mr. Marshall, Czinki is not concerned with gabions at all, but with little baskets for supporting landscaped and planted banks intended to deaden traffic or other noise. I have left this seemingly fundamental difference between Czinki and the claim to the end because there may be a clerical error in the documentation’s description of the dimensions converting centimetres into millimetres. If it is not a mistake, Mr. Platts- Mills can rightly add as a further distinguishing feature of Czinki that, concerned as it is with small boxes, it discloses no prior gabion art of the order or nature of that in issue here.
48. It is plain from Oliver LJ’s formulation of the test in Windsurfing, that the question whether an invention was obvious, that is, involved no inventive step over the prior art, is a question of mixed fact and law, and to the extent that it is one of fact, also one of degree - a jury-type question. Accordingly, an appellate court should be slow to reverse the findings of the trial judge and should not generally disturb them unless they flow from an error of principle or are otherwise clearly unsustainable. See e.g. Biogen v. Medeva [1997] RPC 1, per Lord Hoffmann at 45, HL; Raychem Corp.’s Patent [1999] RPC 497, per Aldous LJ at 516, CA; and Pro Sieben Media v. Carlton UK TV [1999] FSR 610, per Robert Walker LJ at 618-619, CA.
49. I see no basis on which this Court could properly interfere with the Judge’s finding that the claim was not obvious over the prior art as disclosed by Czinki, whatever the size or intended use of the latter. In my view, on the evidence before him, he was entitled to conclude that the skilled reader would not have regarded multi-cavity gabion structures of the hinged sort encompassed by the Hesco Bastion claim as obvious in light of the prior art.
50. Accordingly, I agree with the Judge that the Hesco Bastion patent is valid and that Maccaferri has infringed claim 1 of it. I would dismiss the appeal.

Lord Justice Robert Walker:

51. I agree.

Sir Christopher Slade:

52. I also agree.
Order: Appeal dismissed. Minute of Order to be lodge. (Order not part of approved judgment)