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Update on doctrine of equivalents in the UK

Date: 15 December 2020

Since the UK Supreme Court’s (UKSC) decision in Actavis v Lilly [2017] UKSC 48, we have had to get used to a doctrine of equivalents in the UK.

One Patents Court decision that hinged on the new doctrine is particularly notable, is the Court applied the doctrine to disregard entirely an element of the granted patent claim (something unheard of before I). The case in question is Excel-Eucan Ltd v Source Vagabond Systems Ltd [2019] EWHC 3175 (Pat).


It related to a patent for an ammunition bag known as the “Link-Tail” (GB 2489116). The bag holds linked rounds of ammunition mounted onto a long piece of webbing to enable easy feeding into a machine gun. Instead of having a zipped opening running the length of the bag through which the linked rounds could be introduced horizontally after being folded. The Defendant’s bag had an opening at one end, through which the linked ammunition could be fed vertically and allowed to concertina within the bag.


Thus, the defendants’ bag did not have "an openable closure extending substantially from the first end to the second end“ as claimed. The parties agreed that it did not fall within the scope of the patent as a matter of normal interpretation.

Excel said the clever bit was the “plug and play” functionality of the bag, which enabled linked ammunition to be directly fed out of the bag into the gun. The judge agreed. Approval by the Ministry of Defence as a substitute was compelling evidence that it achieved the same result as the Link-Tail.

The bag from Source Vagabond simply used a method of loading the linked rounds which did not require an openable closure, and the same method of loading could be used with the Link-Tail. The linked rounds in both bags would end up sitting in a folded or concertina formation. The Court found that skilled person would not have concluded that “the openable closure …” was an essential requirement.

“Link-Tail” is used with linked ammunition fed straight from the bag into the gun, webbing-side up. There was debate over the significance of whether the bag might be loaded upside down. The judge found that the opening of the bag did not dictate which way round the ammunition was loaded; both bags could be loaded horizontally and/or vertically and substantially the same result was achieved. She was satisfied that loading the defendant’s bag vertically would achieve substantially the same result in substantially the same way as loading the claimant’s bag horizontally.



Having no doctrine of equivalents gave some certainty to advising on patent infringement prior to 2017. We had “purposive construction” and decades of case law to guide us. Throwing that out the window leaves the potential infringer having to second guess what is the “clever bit” upon which everything depends and beyond which nothing is important.
In this case, one might reasonably have thought that quick loading of the bag might be as important as rapid unloading. Source Vagabond were damned by their own success in winning the MoD contract. Of course theirs was cheaper – it had no elongate zip – but it was apparently a suitable equivalent.

And what about equivalents to the prior art? Does the prior art have the same elasticity of disclosure? Well – not according to Mr. Justice Arnold in Generics (UK) Ltd (t/a Mylan) v Yeda Research and Development Company Ltd [2017] EWHC 2629 (Pat). The law on novelty has not changed and it would take another Supreme Court decision to change it.

And what about a Formstein defence? This has long been available in Germany. It's a squeeze argument. If a product or process is found to infringe a patent by “equivalent means”' under the doctrine of equivalents, but the equivalent would have lacked inventive step over the prior art at the priority date, then it is deemed to fall outside the scope of the claim. Does this apply now in the UK? The possibility is recognized in Technetix BV v Teleste Ltd [2019] EWHC 126 (IPEC), but that was a case before the Intellectual Property Enterprise Court and the patent was invalid for other reasons anyway. Formstein is definitely a defence that needs considering. Logically the scope of equivalents would be circumscribed by such prior art or the patent would be invalid. The patentee cannot run with the fox and hunt with the hounds.


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