Manual of Patent Practice

Section 125: Extent of invention

Sections (125.01 - 125.25) last updated: September 2017.


s.130(7) is also relevant

Section 125 is intended to have, as nearly as practicable, the same effect as the corresponding provisions of the EPC, PCT and CPC.

Section 125(1)
For the purposes of this Act an invention for a patent for which an application has been made or for which a patent has been granted shall, unless the context otherwise requires, be taken to be that specified in a claim of the specification of the application or patent, as the case may be, as interpreted by the description and any drawings contained in that specification, and the extent of the protection conferred by a patent or application for a patent shall be determined accordingly.


This sub section sets out the meaning of an invention as that specified in a claim as interpreted by the description and any drawings, the protection conferred being determined accordingly. (The words “for a patent” in s.125(1) have apparently been inadvertently transposed and should follow the word “application” (first appearance), so then the sub­ section should read: “For the purposes of this Act an invention for which an application for a patent has been made or ….. etc”). It thus concerns the way in which the specification should be construed in this respect but does not impose any requirement with which the applicant must comply. Objection therefore should not be raised by the examiner under s.125(1) as such, although its provision may sometimes usefully be referred to when objecting on other grounds, eg under s.14(5). For example when a claim read on its own appears to be clear and to define the invention, such an objection under s.14(5) may arise if there is matter in the description which is inconsistent with the claim or in some other way casts doubt on the true scope of the invention, see 14.88.




[moved to 125.17.1]


[moved to 125.17.2]



Biotechnological inventions


[moved to 125.27]

Section 125(2)

It is hereby declared for the avoidance of doubt that where more than one invention is specified in any such claim, each invention may have a different priority date under section 5 above.


If a claim is construed to specify more than one invention, the priority date of each invention should be determined separately. Note, partial priority may arise (see the chapter on section 5, particularly 5.20 to 5.25.3.

Section 125(3)
The Protocol on the Interpretation of Article 69 of the European Patent Convention (which Article contains a provision corresponding to subsection (1) above) shall, as for the time being in force, apply for the purposes of subsection (1) above as it applies for the purposes of that Article.

The Protocol on the Interpretation of Article 69 of the EPC


Article 69(1) of the EPC corresponds to s.125(1) of the Act and reads:-

The extent of the protection conferred by a European patent or a European patent application shall be determined by the terms of the claims. Nevertheless, the description and drawings shall be used to interpret the claims.


Both Article 69 of the EPC and s.125(1) of the Act should be construed in the light of the Protocol on the Interpretation of Article 69 of the EPC, which reads:

Article 1
General principles
Article 69 should not be interpreted as meaning 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. Nor should it be taken to mean 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 patent proprietor has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patent proprietor with a reasonable degree of legal certainty for third parties.

Article 2
For the purpose of determining the extent of protection conferred by a European patent, due account shall be taken of any element which is equivalent to an element specified in the claims.





General approach to construction


The reference in the first sentence of the Protocol to “resolving an ambiguity” rejects a literal approach to the construction of patent claims, where words were given their “natural and ordinary meaning” of words, ignoring their context or background unless they were ambiguous. The courts even prior to the Protocol were instead favouring a purposive construction of claims, by giving effect to what would have been understood by the notional addressee. In Catnic Components Ltd and another v Hill and Smith Ltd [1982] RPC 183, Lord Diplock stated (at page 243):- “A patent specification should be given a purposive construction rather than a purely literal one derived from applying to it the kind of meticulous verbal analysis in which lawyers are too often tempted by their training to indulge”.


The skilled reader is taken to suppose that the patentee knew some patent law – that his claim is for the purpose of defining the monopoly and that it should be for something new, as held by the Court of Appeal in Virgin Atlantic Airways Ltd v Premium Aircraft Interiors UK Ltd [2010] RPC 8. Knowledge of that may well affect how the claim is construed. For instance, the patentee would not be expected to have claimed what he had expressly acknowledged was old.



Relationship between the Protocol and the Catnic principle



Equivalents as a guide to construction and the Protocol questions




In approaching the construction of the claims the specification as a whole should be read to obtain the necessary background, and in some cases the meaning of the words used in the claims may be affected or defined by what is said in the body of the specification. In Palmaz’s European Patents (UK) ([1999] RPC 47, upheld on appeal [2000] RPC 631) Pumfrey J held that words of degree such as “thin” must take their meaning from the context. Different meanings could not be attributed either to exclude acknowledged prior art or to be consistent with representations made by the patentee’s patent attorneys in a letter to a patent office. Another example is Glatt’s Application [1983] RPC 122 at page 129, where Whitford J considered that if a particular claim were looked at alone, it would not be assumed that a certain fabric was one which was in itself necessarily and inherently air-permeable. However, against the description of the invention in question “on its true construction the claims of the specification could properly only be read as being limited to an article suitable for conditioning fabrics comprising a flexible woven or non-woven air-permeable web”.


In Hoechst Celanese Corp v BP Chemicals [1999] FSR 319 the Court of Appeal held that there was no rebuttable presumption that words in a patent specification which could have a technical meaning did have that meaning. The court was entitled to hear evidence on the meaning but thereafter had to decide on the meaning from the context in which they were used. See also 14.111 with regard to words used in a claim which are given a special meaning by the description. Caution should be used in considering the purpose or advantage of the invention. In Union Carbide Corp. v BP Chemicals Ltd [1999] RPC 409, it was held that where a stated advantage of the invention was that certain equipment was not required, the fact that a person used that equipment did not mean that he was not using the invention as he may have decided to use it badly.

The Protocol and the UK Supreme Court Judgment in Actavis v Eli Lilly


The requirements of the Protocol to give fair protection for the patentee and a reasonable degree of certainty for third parties were considered by the Supreme Court in Actavis UK Limited and others v Eli Lilly and Company [2017] UKSC 48.


Lord Neuberger noted that he did not consider that the last part of the first sentence of Article 1 only enables the description (i.e. the specification) and the drawings to be taken into account when interpreting the claims, in cases where the claims would otherwise be ambiguous. He also noted that it is apparent from Article 2 that there is at least potentially a difference between interpreting a claim and the extent of the protection afforded by a claim and, when considering the extent of such protection, equivalents must be taken into account.


He went on to say that notwithstanding what Lord Diplock said in Catnic Components Ltd and another v Hill and Smith Ltd [1982] RPC 183, a problem of infringement is best approached by addressing two issues, each of which is to be considered through the eyes of the notional addressee of the patent in suit, i.e. the person skilled in the relevant art. Those issues are:

(i) does the variant infringe any of the claims as a matter of normal interpretation; and, if not, (ii) does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial?

If the answer to either issue is “yes”, there is an infringement; otherwise, there is not. Such an approach complies with Article 2 of the Protocol, as issue (ii) squarely raises the principle of equivalents, but limits its ambit to those variants which contain immaterial variations from the invention. Issue (i) self-evidently raises a question of interpretation, whereas issue (ii) raises a question which would normally have to be answered by reference to the facts and expert evidence.


It was further held in Actavis that to conflate these two issues as a single question of interpretation, as had been done by Lord Hoffman in Kirin-Amgen v Hoescht Marion Roussel Ltd [2005] RPC 9, following his approach in Improver Corporation v Remington Consumer Products Ltd [1990] FSR 181 (which itself had followed Lord Diplock’s analysis in Catnic) is wrong in principle, and can lead to error. Instead, issue (ii) involves not merely identifying what the words of a claim would mean in their context to the notional addressee, but also considering the extent if any to which the scope of protection afforded by the claim should extend beyond that meaning.

The Protocol Questions


In Improver Corporation v Remington Consumer Products Ltd [1990] FSR 181, Hoffmann J formulated Lord Diplock’s approach in Catnic into three questions which the court should ask itself. These have subsequently become known as the ‘Improver’ questions, and in Wheatley v Drillsafe Ltd [2001] RPC 7 were re-named by the Court of Appeal, the ‘Protocol questions’. In Actavis it was emphasised that these questions are guidelines, not strict rules that provide helpful assistance in determining whether a variant infringed. The UKSC in Actavis did however reformulate the questions as follows:
(i) Notwithstanding that it is not within the literal meaning of the relevant claim(s) of the patent, does the variant achieve substantially the same result in substantially the same way as the invention, i.e. the inventive concept revealed by the patent?
(ii) Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?
(iii) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?

In order to establish infringement in a case where there is no literal infringement, a patentee would have to establish that the answer to the first two questions was “yes” and that the answer to the third question was “no”.


The first Improver question, which asks whether the variant has a material effect on the way in which the invention works, is a question which was framed in the context of a mechanical patent, and is not wholly aptly expressed for every type of case. However, in practice, the question as framed by Hoffmann J, with its emphasis on how “the invention” works, should correctly involve the court focussing on the “the problem underlying the invention”. In effect, the question is whether the variant achieves the same result in substantially the same way as the invention. If the answer to that question is no, then it would plainly be inappropriate to conclude that it could infringe. If, by contrast, the answer is yes, then it provides a sound initial basis for concluding that the variant may infringe, but the answer should not be the end of the matter.


The reformulated second question should also apply to variants which rely on, or are based on, developments which have occurred since the priority date, even though the notional addressee is treated as considering the second question as at the priority date. It seems right in principle to have the same question, including the same assumption (i.e. that the variant works) for all cases. While the notional addressee may answer the reformulated second question affirmatively even where the variant was unforeseeable at the priority date, he is less likely to do so than in relation to a variant which was unforeseeable as at that date.


If the variation represents an inventive step, while it may render it less likely that the patentee will succeed on the second reformulated question that alone should not necessarily prevent the resultant variant from infringing the original invention.


The third Improver question as expressed by Hoffmann J is whether the notional addressee would 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. Although the language of the claim is important, consideration of the third question certainly does not exclude the specification of the patent and all the knowledge and expertise which the notional addressee is assumed to have. Further, the fact that the language of the claim does not on any sensible reading cover the variant is certainly not enough to justify holding that the patentee does not satisfy the third question. Hence, the fact that the rubber rod in Improver could not possibly be said to be “an approximation to a helical spring” was not the end of the infringement issue. When considering the third question, it is appropriate to ask whether the component at issue is an “essential” part of the invention, but that is not the same thing as asking if it is an “essential” part of the overall product or process of which the inventive concept is part. Hence in Improver the question was whether the spring would have been regarded by the addressee as essential to the inventive concept, or inventive core, of the patent in suit. Finally when one is considering a variant which would have been obvious at the date of infringement rather than at the priority date, it is necessary to imbue the notional addressee with rather more information than he might have had at the priority date.


In Actavis UK Limited and others v Eli Lilly and Company [2017] UKSC 48, the Supreme Court found that permetrexed dipotassium would infringe a claim to permetrexed disodium because the skilled person would understand that disodium “was the only permetrexed salt on which the experiments described in the specification had been carried out” and that “it does not follow that the patentee did not intend any other permetrexed salts to infringe”. The Supreme Court went on to say that this suggestion “confuses the disclosure of the specification of a patent with the scope of protection afforded by its claims”.





Application of the Protocol questions







Extent of Protection and the Protocol: Summary





Prosectution History


In Actavis it was held that it is appropriate for the UK courts to adopt a sceptical, but not absolutist, attitude to a suggestion that the contents of the prosecution file of a patent should be referred to when considering a question of interpretation or infringement. However, given that the contents of the file are publicly available and are unlikely to be extensive, there will be occasions when justice may fairly be said to require reference to be made to the contents of the file. However, not least in the light of the wording of Article 69 EPC 2000, which is discussed above, the circumstances in which a court can rely on the prosecution history to determine the extent of protection or scope of a patent must be limited. The Court held that reference to the file would only be appropriate where (i) the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point, or (ii) it would be contrary to the public interest for the contents of the file to be ignored. The latter would be exemplified by a case where the patentee had made it clear that he was not seeking to contend that his patent, if granted, would extend its scope to the sort of variant which he now claims infringes.

Biotechnological inventions.


Schedule A2 to the Act was introduced by the Patents Regulations 2000 (2000 SI No 2037) as part of the implementation of Directive 98/44/EC on the legal protection of biotechnological inventions. Paragraphs 7 to 10 of the Schedule set out certain rules for the construction of claims which relate to biological material or to processes that enable biological material to be produced - see 76A.07-09.