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UK Law Update


An Important UK Decision Regarding Patent Priortiy Claims

Jul 2, 2009

From the Marks & Clerk Newsletter on 14 June 2009 (

News Item

Priority - unity of applicants is essential

14 June 2009

The UK Patents Court has ruled that there must be strict unity of applicant as between a first patent filing and a later filing which claims priority from the first application - Edwards Lifesciences v Cook Biotech 12 June 2009. This unity must exist at the date of the later filing. An assignment of priority right after the later application has been filed will be of no effect.

Many patents claim priority from an earlier application filed not more than one year before the later application. Filing a single initial application gives the inventor a year in which to file further applications, all claiming priority back to the original date. Most disputes about priority centre on whether matter has been added in the later application. This is a technical issue which involves comparison of the two applications. If matter has been added, priority will be lost.

It is rare for priority to be challenged on the basis that even though the two applications are the same, there is a lack of unity of applicant as between the earlier and later filings.

The origin of international recognition of priority right derives from the Paris Convention. Article 4A(1) states: “Any person who has duly filed an application for a patent …..or his successor in title, shall enjoy, for the purpose of filing in other countries, a right of priority….”

In Edwards v Cook the priority application was filed in the USA by three individual inventors – A, B and C. The Convention application was filed one year later by a company, Cook, which was the employer of A but not of B and C. B and C later executed an assignment to Cook of all relevant rights, but this was well after the expiry of the Convention period, although before the grant of the patent. The patent was validly granted to Cook, but the question arose as to whether Cook was successor in title to all three inventors for the purpose of lodging the later application claiming priority from the earlier filing.

The UK Patents Court held that although Cook was successor in title to A it was not, at the date of filing the later application, successor in title to B and C and therefore disentitled to claim any priority. The consequence was that an intervening item of prior art was admissible on which to attack the patent.

The court also held that inventor A was not “a person” who had “duly filed an application for a patent” within the meaning of Article 4A(1) of the Paris Convention. He was one of three. The “person” therefore comprised all three inventors. They or their successors would have been entitled to file the later application, but one of them acting alone (or his successor) was not.

This decision means that any question as to the ownership of the original invention, and entitlement to priority based on an earlier filing, has to be sorted out by assignment or other means before the date of the later filing. If it is not, then the earlier priority will be lost, even though the person to whom the patent is granted is duly entitled to the grant.

A further practical issue can arise from this ruling. A patent application can be cited as novelty-destroying under Section 2(3) Patents Act 1977, as being later-published prior art but having an earlier priority date than the patent in suit. Advisors looking at the entitlement to that earlier priority have tended to regard it as a straight technical exercise, involving comparison of the earlier and later applications. But anyone citing a patent application under Section 2(3) would have to satisfy the court that there is unity of title, such that the cited application is entitled to its claim to priority. This could be difficult where the cited application is owned by a third party and the priority filing was by a different person or entity. This is particularly so where the citation derives from a US application. In the USA applicants must be individual inventors and not employers or other entities claiming entitlement. Later applications outside the USA will usually be filed in the name of the company. The party citing the application will bear the burden of proof that there was unity of applicant before the later filing.

For further information contact your usual Marks & Clerk attorney or solicitor, or Gregor Grant at