In an unexpected development, the UK Supreme Court has overturned well-established UK practice on infringement, formulating a new infringement test that introduces a doctrine of equivalents into UK practice.

Previously, it was settled that infringement in the UK depended only on the claim as properly interpreted. There was no separate doctrine of equivalents. Something falling outside the literal scope of a claim only infringed if the claim, on a proper purposive construction, should be understood as covering it. It followed from this that what infringed a patent would have anticipated the patent if it were prior art. All this has now changed.

This significant development will create more legal uncertainty in the UK, but can be seen as a step towards global harmonisation, bringing UK infringement practice more into line with, e.g., German and US practice.


Actavis UK Limited and others (‘Actavis’) sought a declaration of non-infringement in respect of its proposed products in respect of Eli Lilly and Company’s  (‘Lilly’) patent in the UK, France, Italy, and Spain.  Actavis argued that their products do not infringe because the claims of the patent are limited to a specific pemetrexed salt, namely pemetrexed disodium, and the Actavis products contain either pemetrexed diacid or different pemetrexed salts.  By contrast, Lilly argued that the Actavis products represent the essence of the teaching and claim of the patent.

The UK’s law on patent infringement has, to date, relied on the ‘Improver’ test, under which a ‘purposive construction’ is applied.  Under this approach, the question is always what the person skilled in the art would have understood the patentee to be using the language of the claim to mean. For this purpose, the language he has chosen is usually of critical importance.

A new infringement test

In Actavis UK Limited & Ors v Eli Lilly and Company (1), Lord Neuberger returned to first principles, considering Article 69 of the European Patent Convention(2) and the protocol on the interpretation thereof(3), including Article 2 which sets out that “[f]or 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.”

Reviewing both domestic and foreign case law, Lord Neuberger concluded that new principles were required to ensure a balance between fair protection for the patent proprietor and a reasonable degree of legal certainty for third parties.  Discussing what he considered to be weaknesses in the ‘Improver’ questions, he reformulated the questions into the following new test:

(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”.

Thus, anything falling within the language of the claims will be held to infringe, but, importantly, any variants that do not meet this criterion may nevertheless be held to infringe, provided that questions (i) and (ii) can be answered in the positive and question (iii) in the negative.

Whilst the Court of Appeal had applied the Improver test, under which the notional addressee should not be treated as knowing that the Actavis products would work, the new test imparts this knowledge unto the notional addressee. With regard to part (iii) of the new test, Lord Neuberger emphasised the need to give weight to Article 2 of the Protocol.  Applying the new test to the facts before him, Lord Neuberger provisionally concluded that Actavis’ proposed products would directly infringe Lilly’s claim in the UK.

Actavis had also sought a declaration of non-infringement in respect of France, Italy and Spain. After reviewing the domestic law of these countries, Lord Neuberger held that there would also be direct infringement in these countries.

Prosecution history

The claims at issue were limited during prosecution of the patent application from an ‘anti-folate’ (a class of compounds) to the specific compound ‘pemetrexed disodium’.  This raised the question whether the prosecution history may be used when assessing infringement and, if so, whether this would have an effect on the outcome of this case.

A new test was formulated setting out the following conditions under which the prosecution history may be considered:

(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.

Point (ii) would be exemplified by a case where the patentee had made it clear to the patent office 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.

Lord Neuberger concluded that the contents of the prosecution file in this case would not justify departing from the provisional conclusion of direct infringement mentioned above.


Previously, the UK’s approach to assessing infringement seemed to be well-established, as indeed acknowledged at [40] of the judgement. The development of a new infringement test by the UK Supreme Court is therefore not only surprising, but also unsettling for any parties that have until now operated on the understanding that their actions in the UK would be assessed under the ‘Improver’ infringement test.

This new test would seem to bring UK practice more in line with the approach of key continental European courts, such as German and Dutch courts.  This judgement may therefore represent an attempt at harmonisation, perhaps in preparation for the Unitary Patent Court (UPC).

Whilst the new test has been presented at [66] as a “reformulated” version of the ‘Improver’ questions, it does in fact represent a radical departure from previous UK practice.

It is acknowledged under [58] that “there is no doubt that, according to normal principles of interpreting documents, the Actavis products do not infringe the Patent, as in no sensible way can pemetrexed free acid, pemetrexed ditromethamine, or pemetrexed dipotassium mean, i.e. be said to fall within the expression, “pemetrexed disodium” in claim 1 of the Patent”. To those familiar with UK practice it will therefore come as a surprise that the UK Supreme court has formulated a new test under which such products are nevertheless held to infringe.

The new test introduces a doctrine of equivalents in to UK law, with an ex post facto twist. Part (ii) of the test imparts upon the skilled reader knowledge that a variant would achieve substantially the same result as the claimed feature. Given that the testing required to establish whether any particular variant does indeed achieve substantially the same result as the claimed feature can be burdensome (particularly in the pharmaceutical field), this kind of hindsight analysis would seem to be overly generous towards patentees. Indeed, it is acknowledged at [64] that even an inventive variation that is outside of the literal claim scope may be found to infringe under this test.

Perhaps the biggest concern presented by this new test is that it introduces a doctrine of equivalents with regard to the assessment of the scope of protection, whilst seemingly leaving claim construction essentially unchanged.  This could have serious consequences. Under the old test, something falling outside the literal scope of a claim only infringed if the claim, on a proper purposive construction, should be understood as covering it. It followed from this that what infringed a patent would have anticipated the patent if it were prior art. Under the new test, perhaps paradoxically, it would seem that something can be held to infringe a patent even if it was in the prior art.

Another important issue concerns the use of the prosecution history.  Whilst suggesting that recourse to the prosecution history should only be permitted in limited circumstances, the test established by Lord Neuberger will, no doubt, be invoked frequently.  Curiously, part (ii) of the test is rather circular, as it is only by consulting the prosecution history that one can determine whether it would be contrary to the public interest to ignore it!

Conclusions and recommendations

The scope of protection afforded by a claim will now be much more challenging to assess, creating greater uncertainty.  Business practices need to be evaluated carefully in view of this seminal judgement.  Any freedom to operate advice that was provided on the basis of the former practice should be revisited to determine whether it needs to be updated to conform with the new practice.

In dealings before the EPO or UK IPO practitioners should bear in mind that the prosecution history may now potentially be used in UK court proceedings.

For further information, or to discuss the potential impact of this judgement on your business, please contact us at or get in touch with your usual attorney.



“if one cannot depart from the language of the claim when considering those questions, what is the point of the questions in the first place?”