The IPKat thanks Jane Mutimear (Bird & Bird) for tipping him off that the long-awaited House of Lords decision in Kirin-Amgen Inc and others v Hoechst Marion Roussel Limited and others; Kirin-Amgen Inc and others v Hoechst Marion Roussel Limited and others  UKHL 46 is now available here. The leading speech is a majestic opinion by Lord Hoffmann, who, inter alia, effectively deconstructs and rewrites the entire UK law and practice in dealing with two of the biggest and most heavily litigated issues in patent law today:
(i) in what circumstances does a person who does not replicate an invention as described in the claims of a patent infringe that patent and
(ii) how do you know when those circumstances occur?
The case is too long and complex to be conveniently summarised on a weblog, but the IPKat is delighted to serve up some of the most significant bits for your delectation (all references are to paragraph numbers in Lord Hofmann's speech):
* Pre-history. At paras 18 to 22 there is a succinct summary of the law of inexact patent infringement as it stood in the UK and Germany before the adoption of the European Patent Convention
* The Protocol. At paras 23 to 26 his Lordship describes the rationale of the Protocol to Article 69 of the Convention, which reads:
"Article 69 should not be interpreted in the sense that the extent of the protection conferred by a European patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties."This Protocol is a compromise between the wish to provide certainty by interpreting patent claims literarlly and the need to secure a just result by looking at what it would be fair for the patent to protect, regardless of the exact form of words used to couch its claims.
* The "purposive" approach. At paras 27 to 35 his Lordship reviews the evolution of the UK courts' approach to claims construction, both before and after the seminal speech of Lord Diplock in Catnic Components Ltd v Hill & Smith Ltd  RPC 183.
* Equivalents and their equivalents? At paras 36 to 44 the US doctrine of equivalents is discussed. Lord Hoffmann concludes:
"Since the Catnic case we have article 69 which, as it seems to me, firmly shuts the door on any doctrine which extends protection outside the claims. I cannot say that I am sorry because the Festo litigation suggests, with all respect to the courts of the United States, that American patent litigants pay dearly for results which are no more just or predictable than could be achieved by simply reading the claims".* Is Catnic in accordance with the Protocol to Article 69? Paras 45 to 48: in a word, yes.
* Does the UK version of the doctrine of equivalents provide any help? In paras 49 to 52 Lord Hoffmann reviews his own decision in Improver Corporation v Remington Consumer Products Ltd  FSR 181 and that of the Court of Appeal in Wheatley v Drillsafe Ltd  RPC 133. This approach, incorporating what are often called "the Improver questions" or "the Protocol questions" is basically one with which the judges are comfortable, despite its limitations.
* Review of the trial judge's decision: paras 53 to 75 (ending with a review of German and Dutch law).
* Review of the Court of Appeal decision: paras 76 to 77. Lord Hoffmann approves of the Court of Appeal's approach to construction of the patent which, unlike that of the trial judge, actually pays attention to the patent's claims.
* Old test -- valid but unhelpful? From paras 78 to 85 it seems that the applicability of the "Protocol questions" decreases as the factual parameters of the technology to which they are applied becomes ever more complex.
The rest of his Lordship's speech deals with issues of novelty (paras 86 to 101), insufficiency (102-109), breadth of claims (110-117) and sundry technical issues (118-133).
The moral of the story seems to be that, when interpreting patent claims, keep the claims at the heart of your interpretation. As Lord Hoffmann says:
" 72. This is perhaps an appropriate point at which to mention what may appear to be a difference between the German, United Kingdom and Netherlands approach to these questions. It used to be thought that despite article 69 and the Protocol, there remained serious differences between the approaches to construction of the United Kingdom on the one hand and Germany and the Netherlands on the other. And it is true that in the early years of the EPC, there was a view in the German and Netherlands courts that the Convention had made no difference and that the Protocol entitled the courts of Contracting States to go on deciding the extent of protection exactly as before. The position in the Netherlands is described by Professor Brinkhof in the article "Is there a European Doctrine of Equivalence?" (2002) IIC 911 to which I have already referred.The IPKat marvels at Lord Hoffmann's clarity of thought and lucidity of expression. Does anyone in the UK seriously advocate exchanging this sort of quality for an unknown and untried Community patent court?
73. But I do not think that this is any longer true. The highest courts in both Germany (see Batteriekastenschnur  GRUR 903, 904) and the Netherlands (see Ciba-Geigy/Oté Optics (1995) Nederlandse Jurisprudentie 39) have said that the effect of article 69 is to give the claims what the European Patent Office has called a "central role": see BAYER/Plant growth regulating agent  EPOR 257, 261. The Bundesgerichtshof said in the Batteriekastenschnur case that the claims are no longer merely a point of departure but the decisive basis (maßgebliche Grundlage) for determining the extent of protection".