Trialling before filing - the pitfalls.

A recent case heard by the UK Intellectual Property Enterprise Court (IPEC) in Claydon Yield-O-Meter v Mzuri Ltd aimed to clarify what constitutes public prior use. The judgement handed down, on the face of it, appears to be extremely harsh on the patent proprietor, or does it?


The invention relates to a seed drill to be attached to a tractor, as seen below.

At the end of August 2002, a prototype of the seed drill was tested by the inventor, Mr Claydon, in a field on his private farm for ten hours, including travel to and from the workshop, split over two days. 

The issue was whether at any time during those two days the invention was made available to the public.

Mzuri’s case was that Mr Claydon’s prototype could have been observed from nearby roads and from a footpath to which the public had access, enough to obtain an enabling understanding of the invention.

The Law

"State of the art” is defined in Section 2(2) of the UK Patents Act 1977:

“The state of the art in the case of an invention shall be taken to comprise all matter (whether a product, a process, information about either, or anything else) which has at any time before the priority date of that invention been made available to the public (whether in the United Kingdom or elsewhere) by written or oral description, by use or in any other way”.

Importantly, the present case makes reference to the UK case of Lux Traffic Controls Ltd v Pike Signals Ltd [1993], where Aldous J set out the essential principles governing a claim to prior disclosure of an invention:

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. Thus an anticipating description of a book will invalidate a patent if the book is on the shelf of a library open to the public, whether or not anybody read the book and whether or not it was situated in a dark and dusty corner of the library. If the book is available to the public, then the public have the right to make and use the information in the book without hindrance from a monopoly granted by the State”.

Interestingly, the burden-of-proof for public prior use is much higher at the European Patent Office (EPO) where the strict standard of ‘up to the hilt’ (T 472/92) must be proven, i.e. ‘beyond reasonable doubt’ (T 97/94). It is not sufficient that the alleged act is merely probable.

To succeed with a public prior use attack in opposition proceedings before the EPO, an opponent needs to show: (i) when the prior use occurred; (ii) what was made available to the public and (iii) the circumstances of the use, i.e. where, how and by whom (T 1856/11). If any one of these criteria are not met, the attack will fail.

However, since the present case concerns UK revocation proceedings, the question for HHJ Hacon (the UK Judge) to decide upon was whether the testing of the prototype seed drill by Mr Claydon on his private land constituted an enabling disclosure to the public and therefore destroying the novelty of his invention.

The Decision

In his witness statement, Mr Claydon said that he knew that public prior disclosure of his invention would negatively affect his ability pursue patent protection. It was therefore in his mind that he would prevent anyone who happened to be nearby from seeing the prototype.  

Mr Claydon argued that he was in a tractor cab and from that vantage point, he could see anyone in the vicinity before they could see what was happening in the field.  

The Court was also told that there was a public footpath around the outskirts of the field where the testing took place with a hedge about 6 feet high between the footpath and field, but with gaps at three points. 

The Judge gave two “contemporary” examples of the skilled person having access to technical equipment to gain an understanding of the invention and therefore making it an enabling disclosure. Firstly, the skilled person could have had a phone with zoom functionality that would have allowed them to focus in on the invention. Secondly, and somewhat bizarrely, the skilled person could have had a “swarm of drones to hand at the relevant time and place”. However, “the swarm may be liable to give rise to issues of privacy and breach of confidence”.

The Judge ultimately decided that there were periods during which it was likely that a skilled person, standing on the footpath, could have been able to see the prototype in action and been able to deduce the invention from its appearance and from the appearance of soil left in its wake. 

In stark contrast, it was accepted that in the recent decision of E. Mishan & Sons Inc v Hozelock Ltd [2019], if the inventor had become aware of anyone watching his testing of the prototype (an expandable garden hoses), they would either have packed away the equipment and waited until the visitor had left or taken it round to back of their house where it would have been out of sight.

It was noted in the present case, however, that preventing a member of the public from seeing the prototype seed drill would have been a good deal more difficult than hiding a prototype garden hose. The Judge commented that if Mr Claydon had noticed such a person, he did not believe that Mr Claydon could have taken action that would have prevented the skilled person from seeing or inferring each of the features of the invention.

Take-home Message

This judgement at first glace appears extremely harsh on the inventor. Mr Claydon was seemingly testing his prototype on private land on his farm. How else was he supposed to test the seed drill?

The Judge also clearly had sympathy for Mr Claydon, as Paragraph 102 of the judgement commented:

Mr Claydon had to test his prototype, nobody saw any of the testing and I entirely understand why he believed that his invention was not publicly disclosed. Unfortunately for him, in law the prototype was made available to the public”.

Although a decision handed down by the IPEC in the UK, this case could have implications and teachings for inventors worldwide.

The key to this judgment was that Mr Claydon freely admitted that he tested his prototype “in public”. In all likelihood, without this admission, the public prior use argument would not have succeeded. Inventors should not test their inventions in the public domain (nor at least freely admit to doing so) prior to filing a patent application, even if they think it is “in private”. 

Mr Claydon might argue how he is supposed to test a seed drill “behind closed doors”. However, the law is clear. In the present case, even if the skilled person could (not would) have been walking down a remote footpath next to field with a hedge about 6 feet high between the footpath and field (but with gaps at three points) and seen the seed drill in action, this still constitutes an enabling disclosure and public prior use. 

This is aligned with Lux Traffic Controls Ltd v Pike Signals Ltd [1993], whereby there is no need to prove that anybody actually saw the disclosure provided the relevant disclosure was in public.

It is interesting to note that if revocation proceedings were brought before the EPO, the outcome may have been different for Mr Claydon. For example, in T 1410/14, although it was undisputed that  a vehicle with the features of the disputed claim  was driving in a public traffic area in the city of Lodz (the 3rd largest city in Poland) before the priority date, the Board considered that it had not been proven beyond reasonable doubt that a person skilled in the art had the opportunity to recognise all the features of the invention during this act of prior use.

Please do get in touch for further information regarding the above case or for more general advice, we would be delighted to assist!


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