Neutral Citation Number: [2017] EWCA Civ 199
Case No: A3 2016 0533
IN THE COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE HIGH COURT OF JUSTICE
CHANCERY DIVISION
PATENTS COURT
Mr Justice Henry Carr
[2015] EWHC 3298 (Pat)
Royal Courts of Justice
Strand, London, WC2A 2LL

Date: 30/03/2017
Before :

LORD JUSTICE McCOMBE
and
LORD JUSTICE FLOYD
- - - - - - - - - - - - - - - - - - - - -
Between :

	STRETCHLINE INTELLECTUAL PROPERTIES LIMITED	Claimant/
Respondent	
	
- and –
		
	H&M HENNES & MAURITZ LIMITED	Defendant /Appellant	

- - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - -

Guy Burkill QC and Geoffrey Pritchard (instructed by Shoosmith LLP) for the Appellant
Nicholas Caddick QC and Andrew Norris (instructed by Potter Clarkson LLP) for the Respondent

Hearing date: 21 March 2017
- - - - - - - - - - - - - - - - - - - - -
Judgment Approved
Lord Justice Floyd: 
1.	This is an appeal from the decision of Henry Carr J of 20 November 2015 in which he found that the defendant and appellant (“H&M”) had breached the terms of a settlement agreement (“the Settlement Agreement”) entered into by H&M and the claimant and respondent (“Stretchline”).  The appeal, in substance, raises a question of construction of UK patent number 2 309 038 (“the patent”) which underlay the Settlement Agreement. The patent is concerned with tubular fabric, particularly for use in underwired garments such as bras.
2.	The Settlement Agreement came about as a result of proceedings which Stretchline had brought against H&M in 2010 for infringement of the patent. We are not concerned with the detailed terms of the Settlement Agreement. The judge summarised their effect, so far as relevant for our purposes, at paragraph 8 of his judgment:
“So, in summary, H&M agreed not to deal in any product which fell within any of the claims of the Patent and paid an agreed sum by way of costs to Stretchline. … On this basis, the parties settled their differences and entered into the Settlement Agreement.”
3.	The present proceedings were commenced on 28 March 2013.  Stretchline alleged that H&M were again selling bras which fell within the claims of the patent.  It was, accordingly, asserted that H&M was in breach of the Settlement Agreement or that it had infringed the patent.  In addition, H&M asserted that the patent was invalid and counterclaimed for its revocation.  In October 2014, H&M’s invalidity defence and counterclaim were struck out by Sales J (as he then was) because the Settlement Agreement precluded H&M from raising the issue of validity in these proceedings. That decision was confirmed on appeal: [2015] EWCA Civ 516.  Although Stretchline’s infringement claim was not struck out (as H&M had not asked that it should be), following the Court of Appeal’s judgment, Stretchline discontinued its infringement claim and thenceforth relied only on breach of the Settlement Agreement. 
The issue between the parties
4.	The patent is concerned, in particular, with tubular fabric used to encase underwires in garments such as bras. The patent states that there was a known problem with such fabric tubing at the priority date (page 1 lines 12-19):
“A considerable problem with known fabric tubing for underwires is that the ends of the underwires can penetrate the tubing, either during the course of garment manufacture or in use by a wearer.
At present, a significant proportion of brassiere (bra) manufacturers (sic) products are returned because of protrusion of the underwire through the fabric tubing.”
5.	Claim 1 of the patent is a process claim which, it should be noted, is in broader terms.  It specifies:
“a method for making a tubular fabric comprising providing a support yarn and an elastomeric yarn; characterised in that a fusible yarn is also provided and in that the yarns are formed into a tubular fabric whereby the fusible yarn is arranged within the fabric tube so that it is capable of forming a penetration barrier.”
6.	The dispute between the parties concerns the correct interpretation of the final words of this claim.  Stretchline contends that the patent is claiming a structure which, by reason of bonding of the fibres, is better able to resist penetration (for example by wire) than would be the case if the fusible yarn had not been used.  This can be achieved if the fusible yarn simply spreads itself over surrounding fibres to form points of adhesion or bonding between those fibres. H&M contends that the patent requires that the fusible yarn must create an identifiable, substantially continuous layer-like barrier or lining. On this basis, points of adhesion are not sufficient. The layer created must form a substantially continuous liner which provides the required penetration barrier. It is common ground that if H&M’s construction is the correct one, there is no infringement.  If the judge’s construction is correct, there is.
Approach to construction
7.	The approach to construction of patent specifications is well settled.  The object of the exercise is to determine what the skilled person would understand the patentee to be using the language of the claim to mean: see per Lord Hoffmann in Kirin-Amgen Inc. and others v Hoechst Marion Roussel and others [2005] RPC 9.  See also the summary of principles in Virgin Atlantic Airways v Premium Aircraft Interiors UK  [2010] RPC 8 at [5]. 
8.	A particular issue which arises in the context of the present case concerns whether one should be persuaded to reject a particular construction because of the legal consequences which that construction has for the validity of the patent.  The issue is important because H&M are not entitled to challenge the validity of the patent directly.    In Beloit v Valmet (No 2) [1995] RPC 255 at 270, Jacob J, as he then was, explained that it was not normally legitimate to construe claims using the prior art, because there was normally no reason to suppose that the patentee, when he set the limits of his claims, knew of any individual item of prior art. However, he continued:
“Of course the position is different if the prior art is specifically acknowledged in the patent. The purposive construction would lead to a construction of a claim which did not cover that acknowledged prior art: it can hardly have been the inventor’s purpose to cover that which he expressly recognises was old.”
9.	Jacob J’s conclusion that a patentee would not readily be taken to be intending to claim something which he expressly recognised as old is, as Henry Carr J pointed out, no more than an application of the well-known principle referred to by Lord Russell in Electric and Musical Industries v Lissen (1936) 56 RPC 23 at 39:
“ … if possible, a specification should be construed so as not to lead to a foolish result or one which the Patentee could not have contemplated.” 
10.	Mr Burkill QC, who appeared on behalf of H&M with Mr Geoffrey Pritchard, relied on a passage in Terrell on the Law of Patents 18th Edition at 9-254 which suggests that the same approach may be appropriate where the consequence of a construction would be that the patent would be obvious in the light of common general knowledge.  However, in Adaptive Spectrum v British Telecommunications Ltd [2014] EWCA Civ 1462 I had some reservations about that:
“ … as soon as one departs from documents specifically acknowledged in the specification, the skilled reader has no basis for assuming that the patentee was aware of the document in question. Still further, where the objection is one of obviousness rather than lack of novelty, a value judgment is involved on which widely differing views are possible. It is true that if the document is said to form part of the common general knowledge, it might be said to be more likely that the patentee is aware of it. But a patentee may have been isolated from the common general knowledge, or may, despite the later finding of obviousness, have genuinely believed that he had made an invention over it.”
11.	I remain of the view that the fact that a particular construction may lead to a conclusion that the invention is obvious in the light of the common general knowledge is likely to be a much less potent factor weighing against that construction than a specific acknowledgement of prior art onto which the claim will read directly. 
12.	Finally, it is of course well settled that one cannot disregard obviously intentional elements in a claim. Deliberate limitations must have a meaning: see STEP v Emson [1993] RPC at 522 summarised in Virgin Atlantic at paragraph 5(vii).
The patent
13.	I have already explained the problem addressed by the patent.  It is the need to provide a tubular fabric which is resistant to penetration by wire, so as to prevent the underwires from protruding as a result of manufacture or use.  The principal claims of the patent are, however, not limited to tubular fabric for that purpose, but extend to all tubular fabric having the specified yarns, provided the penetration barrier requirement is met.  
14.	At page 2 lines 6-7 the specification states:
“By “fusible yarn” we include the meaning that the yarn can be melted at a predetermined temperature and cooled to adhere to the support yarn.”
15.	The specification explains that whilst fusible yarn in the form of monofilaments could be used, a multifilament yarn is preferred “because on melting it spreads more easily on the fabric”. A monofilament produces a “less even spread which may be less comfortable to a wearer of a finished garment”. The specification continues at page 2 line 28 to page 3 line 1:
“Preferably, the fusible yarn is treated by heating whereby it melts and spreads over the interior surface of the tubular fabric. On cooling, the fusible yarn adheres to the other yarns of the fabric to produce a tubular fabric having a durable inner lining of the melted fusible yarn.”
16.	The reference to “a durable inner lining” is much relied on by H&M in support of their construction.  There is other use of the expression “a durable inner lining”, or similar language, in the specification.  At page 7 lines 9 to 13,  page 8 lines 6 to 8 and page 12 lines 5 to 12 we find the following (with my added emphasis):
“Preferably, the method of the invention comprises a further step of treating the tubular fabric by heating to melt the fusible yarn so that it spreads over the tubular fabric and is capable of forming a penetration barrier. On cooling, the melted yarn adheres to the other yarns of the fabric to form a durable inner tube lining.
…
The fabric tubing produced in accordance with the invention has a durable inner lining of fusible yarn which is extremely resistant to penetration by underwires.
…
 “The preferred method of the invention produces a tubular fabric comprising a polyamide yarn, and elastomeric yarn and a fusible polyamides yarn, preferably Grilon K-85, capable of forming a penetration barrier within the fabric tube. Whilst such a product may be a valuable commercial product in itself, it is preferably subjected to a further heat treatment step to provide a durable lining of fused polyamides on the interior surface of the fabric tubing.”
17.	Returning to the sequence of the specification, at page 3 lines 19-25 it explains:
“A skilled person will understand that a fusible yarn of the invention is intended to include any yarn which can melt at a predetermined temperature, preferably 75-90° C, and adhere to other yarns of the fabric to form a penetration barrier. On cooling the melted fusible yarn preferably produces a coating which has a temperature in excess of the predetermined temperature and preferably in excess of 100° C”
18.	In contrast, the function of the elastomeric yarn is to lend the fabric a desirable degree of flexibility or “give”. The function of the support yarn is self-evident.
19.	At page 6 line 28 there is a description of the preferred ranges of percentage by weight of the different yarns.  The fusible yarn is said to be 5-15%, and especially approximately 8% of the fabric weight.  If a monofilament yarn is used, more yarn may be necessary to give satisfactory spreading, and so the preferred range is 5-20%, especially 10%. 
20.	A passage at page 8 lines 10 to 17 reports on independent tests which are said to have demonstrated that fabric tubing of the invention is over twice is resistant to underwire penetration as conventional fabric tubing. The specification continues:
“In contrast to known fabric tubing, the advantageous resistance to penetration property of the fabric tubing of the invention makes it well-suited for use in underwired garments intended for machine rather than hand washing …”
21.	The specification contains descriptions of the process for making the tubular fabric incorporating the fusible and elastomeric yarns, and the subsequent heat treatment of the tubular fabric.  Example 3 at page 14 onwards reports on the measurement of penetration force through the fabrics using a strain gauge tester and a “90’s medium ball needle” to represent an underwire.  The example concludes:
“Comparing the forces required to penetrate [samples of tubular fabric according to the invention] it is clear that the fabric of the invention is two or three times more resistant to penetration than a known fabric used for receiving underwires in bras.”
The judgment of Henry Carr J
22.	The judge first pointed out two aspects of the common general knowledge which were of particular importance, in his view, when considering the disclosure of the patent. The first, which he dealt with at paragraph 28, concerned the known properties of fusible yarns. Fusible yarns had been well known for many years before the priority date. They were also known as “binding yarn”, “bonding yarn” and “barrier yarn”. The “normal function” of fusible yarn is, on melting and cooling, to bond fibres together within a fabric in order, for example, to strengthen the material. It was known to act as an adhesive, for example, at points of contact between weft and warp.
23.	The second point which the judge made about the common general knowledge was that the skilled person would also have known as part of his common general knowledge that it was impossible to form a continuous, discrete layer or liner from fusible yarn in a tubular fabric, particularly in the case of woven fabric as described and shown in the patent. A preferred fusible yarn referred to in the patent was “Grilon”. Grilon has high viscosity. The skilled person would know that a high viscosity was needed because low viscosity polymer would simply leak out of the fabric structure. However high viscosity polymer would not form a continuous layer. This had been the view of Prof Shishoo, Stretchline’s expert witness, who had said:
"A high viscosity is needed because a lower viscosity would mean that the molten polymer would simply leak out of the fabric structure. This would be particularly problematic for a tubular fabric; instead of fusing the yarns of fabric together the polymer would cause the inner surfaces of the tube to stick together defeating the object of having a tubular fabric. Therefore a high viscosity is required. However, with a polymer of higher viscosity, the woven structure of the fabric will impede the polymer flow to the extent that it simply would not form a continuous layer of the polymer. In fact, I do not think it would be possible to include enough fusible yarn within the fabric to create a continuous layer and certainly not if one uses the preferred quantities of fusing yarn referred to in the Patent (namely 5% to 15%). Indeed it would make no commercial sense to try. In my opinion these facts would have been apparent to the skilled reader."
24.	The judge explained his conclusions further in paragraphs 30 and 31 of his judgment:
“30. Prof. Ellis estimated that 50% of fusible yarn within the fabric would be required to form a discrete layer or liner, because the fusible yarn was too viscous to spread widely and its flow would be impeded by the main yarns in the fabric structure. He accepted during cross-examination that he would not expect the fusible material to form a full layer (T3/434/14-436/10). 
31. There is very little dispute on this issue between the experts, but insofar as there is a difference of opinion, I accept the view of Prof. Shishoo. There was no suggestion that Prof. Ellis had actually tried to form a discrete layer in woven fabric using any particular proportion of fusible yarn. I find that skilled person would have known at the priority date that it would not be practical to form a discrete layer from fusible yarn in a woven fabric. Prof. Ellis thought that fusible yarn was about 10 times as expensive as the other yarns used in the invention. Because of the additional cost of such material, it would not make commercial sense to try to form a layer of such material, given that simply including a small quantity as adhesive within the structure would increase the resistance to penetration, and there was no reason to believe that a discrete layer would be any better.”
25.	When reviewing the disclosure of the specification the judge took these aspects of the common general knowledge into account.  Thus, for example, at paragraph 37, the judge deals with the passage in the specification at page 2 line 38 two page 3 line 1:
“It is clear from this passage that the fusible yarn is not intended to form a barrier which is discrete from the rest of the yarns of the fabric. On the contrary, the disclosure is that the fusible yarn will adhere to the other yarns in the fabric on melting, thereby rendering the tubular fabric as a whole more durable. The reference to "durable inner lining" is to the composite of yarns with points of adhesion following melting and cooling of the fusible yarn. Prof. Ellis considered that "the use of fusible yarn in order to bond fibres together to improve fabric durability" was common general knowledge at the priority date (Ellis 1 [32]). The Patent is describing a particular application of fusible yarn, to improve the penetration resistance of tubular fabric.”
26.	Similarly, at paragraph 43 the judge said in relation to the passage of the specification at page 7 lines 9 – 13:
“This passage is relied on by both parties. On the one hand, it is capable of meaning that the penetration barrier must be formed from the fusible yarn on its own.  On the other hand, it is capable of meaning that the penetration barrier is formed by adherence of the melted yarn to other yarns in the fabric, the effect of which is to strengthen the fabric tube.  Having regard to the common general knowledge, and to the entire disclosure of the Patent, in my judgment the latter interpretation is correct.”
27.	Similarly, other passages which referred to a “durable inner lining”, if “taken literally” could support H&M’s construction.  However, “in context, and with the benefit of common general knowledge, they are referring to the increased resistance to penetration of the fabric tubing as a result of adherence of the melted yarn to other yarns of the fabric”. 
28.	The judge expressed his conclusion on construction of claim one in the following way:
“I have reached the conclusion that the skilled person would understand that it is the fabric tube that must resist penetration and the fusible yarn is only effective when it bonds with other yarns to increase the tensile strength of the fabric tube. The claims require that the fusible yarn is (or is capable of being) the cause, or trigger, for formation of the penetration barrier, which comprises the remaining yarns as a composite structure.  The claims do not require the fusible yarn to form a discrete, continuous layer, which the skilled person would know was impractical. Furthermore, it is clear from the description, and from common general knowledge, that an absolute barrier to penetration is not required.  Fusible yarn is used to achieve a higher resistance to penetration than would be the case in conventional tubular fabric, in order to address the problem of underwire protrusion.”
29.	The judge also dealt with H&M’s argument that, on Stretchline’s construction, the skilled person would think that the invention would be obvious over the common general knowledge. Fusible yarn would be being used for its well-known purpose. The skilled person would reject that construction as one which led to a foolish result. The judge was not impressed by this argument for the following reasons:
i)	H&M was precluded, as this court had held, from raising, in its defence, any squeeze between non-infringement and invalidity. As the argument had developed it had become clear to be judge that this was in effect what H&M was arguing for;
ii)	He had reached a clear view as to the correct interpretation of the claim. Had validity been an issue, and had this interpretation led to a finding of invalidity, he would still have been of the same view.
iii)	Even if the argument had been open to H&M, the alleged squeeze between non-infringement and obviousness on the basis of common general knowledge would have failed on the evidence. In that connection the judge concluded at paragraph 68:
“In my judgment, whilst the evidence established that fusible yarn was well-known at the priority date, it did not establish that its use to increase penetration resistance in tubular fabric was common general knowledge at that date. On the contrary, this appeared to be a new use of a known material to solve a long-standing problem.”
H&M’s submissions on the appeal
30.	Mr Burkill drew attention to the fact that both H&M’s construction and Stretchline’s had consequences for the validity of the patent.  He submitted that Stretchline’s construction led to the conclusion, based on the judge’s findings of common general knowledge, that the patent was obvious.  H&M’s construction, if one accepted the judge’s finding that it was impossible to form a continuous layer with the quantities of fusible yarn in the patent, might be said to lead to a finding of insufficiency.  It was therefore necessary to attempt to reach a conclusion on construction before considering the consequences for validity.
31.	Mr Burkill submitted that Stretchline’s construction, which merely involved an overall tubular fabric being more resistant to penetration, gave the word “barrier” no real content.  If the patentee had merely wanted to say that the fusible yarn gave the fabric as a whole a greater resistance to penetration, he could have said so without using the word “barrier”. He relied on the principle, to which I have referred, that words of limitation which had been deliberately chosen had to be given some meaning.
32.	Mr Burkill submitted that the judge had been guilty of the fallacy of the undistributed middle.  Just because a barrier improves penetration resistance, it did not mean that everything which improved penetration resistance was a barrier.  A barrier required something more, and the repeated use of the phrase “inner lining” in the specification indicated what this was.  The barrier was something which had to be “formed” during the process, and there was not a barrier solely because what was there originally is improved. 
33.	Mr Burkill accepted that the term “barrier” did not imply an absolute, and that the effectiveness of a barrier to penetration was to some extent a matter of degree.  However, the fact that there was a range of effectiveness did not mean that one could construe the word in a way which gave it no content at all.
34.	Mr Burkill submitted that it was wrong to look at the principal claims of the patent as if they were limited to a tubular fabric in an underwired bra.  The claims were far wider, and extended to a range of technical fabrics where the use of fusible yarns to improve strength was, he submitted, known.  If technical fabrics having all the features of the claim were common general knowledge, merely to specify their inclusion in a tubular fabric was obvious.  On Stretchline’s construction this was covered by claim 1.  The skilled person would reject that construction as one leading to a foolish result.
35.	The judge’s finding at paragraph 68 that it was not common general knowledge to use fusible yarn to increase the penetration resistance of tubular fabric was inconsistent with his earlier finding that it was common general knowledge that fusible yarn would lead to strengthening of the fabric, even in small quantities.  His earlier conclusion was to be preferred. 
36.	The references to the fusible yarn “adhering” to the other yarns were, Mr Burkill submitted, neutral because, whether the barrier was a separate layer or not, this would still be necessary.  He submitted that the references to  “spreading” supported his construction, as it conveyed the impression of the fused material spreading out over the area of the fabric, as would be necessary if it were to form a continuous layer.  
37.	Mr Burkill also attacked the judge’s reliance on his conclusion that it was not possible to make a layer in the way that H&M’s construction of the patent required.  He submitted, firstly, that it did not matter if it was in fact the case that it would not work.  It would simply follow that the patentee had made an impractical suggestion, which might have led to a finding of insufficiency.  It did not automatically follow that this construction was not what the patentee had intended.  Secondly, Mr Burkill submitted that the judge had gone too far in saying that the skilled person knew from his or her common general knowledge that it was impossible to make such a layer.  The judge’s ultimate conclusion was only that you needed a lot of the material to do it and more than the disclosure of the patent recommended.  It was wrong in principle to hold that something was common general knowledge which had not previously been done.  Moreover the judge had relied on matters of practicality and commercial good sense, which had no place in considering whether something was technically possible.   Mr Burkill did not dispute that the judge was in a position to make a finding of fact that the invention would not work with the low percentages of fibre: but the evidence on which the judge relied did not justify a conclusion that it was common general knowledge. 
38.	Mr Burkill relied in particular on some cross-examination of Prof Ellis who had said that his impression “on reading the patent for the very first time” was that “I would have expected it on first consideration to form a layer”.  He was then asked:
“Q.  Even though you know that is not how fusing yarn works?
A. When working on this later, I would have realised there is not enough to form a continuous layer.”
39.	Mr Burkill suggested that it was not legitimate to construe the patent through the eyes of an expert such as Prof Ellis after he has spent much time on considering what might be made to work.  What he concluded after such a study was not common general knowledge. 
40.	Mr Burkill also showed us some internal documentation, consisting of emails, which he suggested showed technical staff at Stretchline discussing the formation of a barrier layer in a way which implied that they thought the formation of a layer was possible.  
Stretchline’s submissions
41.	Mr Caddick QC supported the judge’s reasoning and conclusions.  He submitted that the case was not about the validity of the patent.  Moreover there was no basis for interfering with the judge’s factual findings as to the common general knowledge.  
42.	Mr Caddick submitted that there were passages in the specification which supported both Stretchline’s construction and H&M’s construction. However, in view of the judge’s conclusion as to the common general knowledge, only Stretchline’s construction made sense of the specification.  The judge had made a clear finding that it was not possible to form a full layer.  What the judge has said about practicality, and the commercial sense of making such a layer were alternative conclusions.  
43.	The references in the specification to an inner lining were apt to indicate that the fusible yarns produced something within the fabric body, as opposed to a separate lining on one surface of the fabric.  It was not possible to produce such a separate lining on one surface from fibres which were interwoven with the other yarns.  The references to the fused yarns adhering to the other yarns of the fabric were neutral, as Mr Burkill accepted.  The references to spreading and coating were also consistent with the normal function of fusible yarn, to spread out over and coat the fibres, without producing a continuous layer. 
44.	So far as the consequences of Stretchline’s construction were concerned, the judge had rightly rejected the suggestion that it was common general knowledge to use fusible yarn to increase penetration resistance in tubular fabric.  In fact H&M had produced no evidence at all of any actual use of fusible yarn in tubular fabric.  Professor Shishoo’s evidence had been clear:
“I can say with certainty that I have no recollection of the idea of using fusing yarn to increase resistance to penetration, or tensile strength, in tubular fabrics being something that was known at the priority date. Indeed, I firmly believe that it was not known at that date.”
45.	The judge’s earlier conclusions about the known uses of fusible yarn to increase strength generally were not in the context of tubular fabrics.  Accordingly the skilled reader of the patent would understand that what was being claimed as inventive was a new use of fusible yarn in relation to increasing penetration resistance in tubular fabrics.  This was not a foolish result which pointed away from Stretchline’s construction.  Moreover, it was far less compelling a reason than that offered against H&M’s construction, namely that the skilled person would not understand how such a construction could possibly work. 
46.	Finally, Mr Caddick submitted that Stetchline’s internal emails did not shed any useful light on whether the skilled person would think that the formation of a continuous barrier from low quantities of fusible yarn was feasible.
Discussion
47.	I start with the judge’s finding about common general knowledge.  I think that it is necessary to distinguish between matters which were part of the common general knowledge, and matters which become apparent to the skilled person from a reading of the patent in the light of common general knowledge.  The judge’s conclusion that it was impossible to form a discrete layer from fusible yarn was, I think, a finding in the latter category, rather than a conclusion that such layers were, in all circumstances, an impossibility.  Thus, in paragraph 29, the judge refers to the case of woven fabric as described and shown in figure 1 of the patent and to the commercial fusible yarn, Grilon, which is used in the examples. In addition, the evidence of Professor Shishoo on which the judge relies in paragraph 29 refers to the preferred quantities of the fusible yarn used in the patent. If the judge were going further and saying that a discrete layer was in all circumstances an impossibility, then I would have agreed with Mr Burkill that he was going too far. 
48.	I am however entirely satisfied that the judge was entitled to conclude, as he did at paragraph 31, that the skilled person would know as a matter of his common general knowledge that it was not practical to form a discrete layer from fusible yarn in a woven fabric without about 50% of fusible yarn.  Prof Ellis was able to make that estimate from his own experience and it was consistent with Prof Shishoo’s evidence.  There is no substance in Mr Burkill’s attempt to suggest that Prof Ellis only reached that conclusion after much work and thought.   His conclusion to the opposite effect was on a very first reading and presumably without much reflection at all. It is true that the judge also recorded points which the witnesses had made about the cost of fusible yarn, but that did not detract from the technical force of their evidence on the central question.    
49.	I do not think that the language of the claim itself is so clear that one is driven inexorably towards Stretchline’s or H&M’s construction.  It is certainly difficult to get out of the claim that it is the fusible yarn, and only the fusible yarn which forms the barrier.  The skilled person would, accordingly, need to go to the specification to understand what sort of barrier the patentee had in mind.
50.	I have recited the parties’ arguments based on passages of the specification, and in particular what they make of the use of “inner lining”, “spreading”, “coating” and “adhering”.   There is certainly enough to suggest that the barrier which the patentee had in mind might be a continuous membrane of fusible yarn.  Equally, there are indications that all that was expected of the fusible yarn was that it should bond to the other fibres and hold them together at points of contact.  However, what this case illustrates is the importance of approaching a patent specification from the viewpoint of the skilled person.  Read as a whole, and with the benefit of the common general knowledge, the specification does not bring to mind a continuous layer.  If the patentee were contemplating such a layer in a woven fabric, then the skilled person would expect to see that correspondingly large quantities of fusible yarn, of the order of 50%, were included.  In my judgment, the common general knowledge about the amount of fusible yarn which would need to be included in woven fabrics to form a continuous layer is a strong indicator in favour of Stretchline’s construction. 
51.	I do not think that Stretchline’s construction involves the logical fallacy of the undistributed middle.  The inclusion of the fusible yarns increases resistance to penetration, by creating a structure within the fabric.  It is entirely logical to describe the fabric including such a structure as a barrier, or as including a barrier.  A barrier is not necessarily a continuous layer of material, nor is there any reason why it may not be formed by a combination of yarns.  Stretchline’s construction does not strike out the word barrier from the claim: it simply gives it a different meaning.  
52.	I was not impressed by any of the Stretchline email material which Mr Burkill sought to rely on.  The judge had the benefit of expert evidence on the issue of what would be considered possible by the skilled person.  Material of this sought would necessarily take second place.  In any event, none of it went as far as Mr Burkill needed it to go. 
53.	It remains to consider whether the judge was right to reject H&M’s argument that, so to construe the claim, would lead to a foolish result on the ground that the invention as claimed would be thought by the reader to be obvious in the light of common general knowledge.  The evidence did not establish any well known use of fusible yarn in tubular fabrics.  In these circumstances we are several steps removed from the example given by Jacob J in Beloit, of a claim which, on a wider construction, would read directly on to an item of prior art referred to in the patent specification, so as to deprive the claim of novelty. The first step is that the consequence is said to be that the claim is vulnerable to an attack based on common general knowledge, not on a document acknowledged in the patent.   The second step is that the patent, so construed, does not read on to the common general knowledge, but is said to lack inventive step in relation to it.  As I said in Adaptive Spectrum, these two points have the effect of substantially weakening the impact of the argument.   The skilled reader would be entitled to deduce no more than that the patentee thought he had made an invention by using fusible yarn to improve penetration resistance in tubular fabrics.   The reader might disagree with that conclusion, but it seems to me to be difficult to conclude that he would think it a foolish result. 
54.	The judge made no finding that it was obvious to use fusible yarn to increase the penetration resistance of tubular fabric.  His finding at paragraph 68 is therefore not inconsistent with his earlier findings as to the known uses of fusible yarn.  It would be wrong to assume against the patentee that the skilled reader would consider it obvious to use fusible yarn in this new context, particularly when it appears that it was not a self-evident solution to the problem when it came up in the context of underwire bras.  Moreover, as the judge recorded as paragraph 67, Prof Ellis did not go as far as to suggest that he thought that the patent was obvious on the basis of common general knowledge.  He expressly disavowed any such suggestion, describing it only as “an answer” to the problem of penetration by the underwires.  It is true that the claim is wider than underwire bras, but there is no reason to suppose that the invention would be considered obvious by the skilled reader when applied to any other type of tubular fabric either. 
55.	Drawing this together, the indicators relied on by Stretchline as to the correctness of its construction are, in my judgment, of far greater persuasiveness than the suggestion that its construction would result in obviousness over the common general knowledge.   The judge was right to view the case in this way, and to construe the claim as he did.
Conclusion
56.	For the reasons I have given, I agree with the judge’s construction of the claim.  I would therefore dismiss the appeal.  
Lord Justice McCombe
57.	I agree.