Insights High Court finds that unobserved trial of seed drill machinery in a field next to a public footpath rendered the patent relating to the invention invalid for prior use



The claimant, Claydon Yield-O-Meter Ltd, makes and sells agricultural machinery. The defendant, Mzuri Ltd, is a company in Worcestershire which competes in the same market.

Claydon claimed that Mzuri had infringed two of its patents: (i) a UK patent entitled “Improved seed drill”; and (ii) a European patent claiming another invention of the same title.

The specification of the UK patent states that the invention relates to a new method and apparatus for planting seed using a seed drilling apparatus pulled by a tractor to produce agricultural crops.

The EU patent claims an invention expressly stated to be an improvement on that of the UK patent.

Mzuri counterclaimed for revocation of both patents. It alleged that the UK patent was invalid on account of prior use by Claydon itself and by reference to a US patent, and that the EU patent was invalid on account of the US patent and another piece of prior art.

Prior use

It was not in dispute that before the priority date of the UK patent, Claydon tested a prototype of its seed drill, which had all the features of claim 16, the particular claim in contention. The prototype was made in Claydon’s farm workshop by Mr Claydon, his brother and a Claydon employee. It was tested in a field for ten hours, split over two days.

There was a public footpath that skirted the edge of the field where the testing took place, which in 2002 was unmarked and unmaintained. There was a hedge about six feet high between the footpath and field, but with gaps at three points.

Mzuri argued that Claydon’s prototype could have been observed from this public footpath, enough to obtain an enabling understanding of the invention.

Mr Claydon gave evidence as to what happened during the two days of testing and the experts gave evidence as to what the skilled person would have been able to determine and infer.

Mr Claydon said in his witness statement that, at the time of the test, it was in his mind that he would prevent anyone who happened to be nearby from seeing the prototype. He was in a tractor cab and from that vantage point could see anyone in the vicinity before they could see what was happening in the field. He discussed what to do with his brother before the tests began, and they decided that, if they saw anyone, they would move away so that such person would not be close enough to see any relevant detail of the prototype.

In fact, there was never anyone present other than Mr Claydon and his brother.


His Honour Judge Hacon found that, subject to the question of validity, the UK patent had indeed been infringed by Mzuri. The issue therefore was whether, at any time during the two days of testing, the invention of claim 16 was made available to the public.

HHJ Hacon noted the essential principles governing a claim to prior disclosure, as set out in Lux Traffic Controls Ltd v Pike Signals Ltd [1993] RPC 107: “It is settled law that to invalidate a patent a disclosure has to be what has been called an enabling disclosure. That is to say the disclosure has to be such as to enable the public to make or obtain the invention. Further it is settled law that there is no need to prove that anybody actually saw the disclosure provided the relevant disclosure was in public. … ”.

It was common ground that for an enabling disclosure, the hypothetical observer is a person skilled in the art who is able to discern details of the invention at the same level of generality as set out in the claim, and that his/her access must be lawful, i.e. trespass is excluded.

In this case, HHJ Hacon said that the evidence on the hypothetical use of technical equipment by the skilled person was not sufficient to make any findings. Therefore, the enablement had to be assessed by reference to hypothetical observation with the naked eye.

HHJ Hacon noted that, in cross-examination, it emerged that the point of public access from which an observer would have been best placed to observe the testing was on the public footpath. Mr Claydon said that the path was very little used in 2002, but that assertion still implied that the public had access to it.

Mr Claydon was asked to assume that he was driving the tractor pulling the prototype when a person appeared behind him at the point from which the photographs were taken. He was asked what he would have done if his brother had spotted this person. He said he would have stopped and, if necessary, lifted the drill and reversed so that all the observer could have seen was the tractor.

HHJ Hacon said that he found it hard to believe that nearly 20 years later Mr Claydon could accurately say with any certainty what he would have done. No doubt it would have depended on the exact circumstances and the impulse of the moment. HHJ Hacon also distinguished the facts from the situation in E Mishan & Sons v Hozelock Ltd [2019] EWHC 991 (Pat), which was a patent infringement claim relating to expandable garden hoses, which included an allegation of prior use by the inventor testing prototypes in his garden, and in which the inventor’s accepted evidence was that if he had become aware of anyone watching, he would have packed the equipment away and waited until the visitor had left. In HHJ Hacon’s view, preventing a member of the public from seeing a prototype seed drill would have been much more difficult than hiding a prototype garden hose.

Assessing the expert evidence, from HHJ Hacon found that there were periods, possibly many, during which it was likely that a skilled person, standing on the footpath at a particular point, would have been able to see the prototype in action and been able to deduce from its appearance and from the appearance of soil left in its wake, features of construction of the prototype including all the features of claim 16. If such a person had been noticed, HHJ Hacon found that Mr Claydon could not have taken action to prevent them from seeing or inferring each of those features.

HHJ Hacon accepted that Mr Claydon had to test his prototype and the fact was that nobody actually saw any of the testing. However, in law, the prototype had been made available to the public. Claim 16 of the UK patent therefore lacked novelty because of the prior use of the invention in August 2002.

Accordingly, Mzuri would have infringed the UK patent had it been valid, but it was invalid. HHJ Hacon also found that the EU patent was invalid, as it lacked inventive step over the prior art. Therefore, there was no infringement. The claim was dismissed. (Claydon Yield-O-Meter Ltd v Mzuri Ltd [2021] EWHC 1007 (IPEC) (22 April 2021) — to read the judgment in full, click here).