On 22 April 2021 the Intellectual Property Enterprise Court (IPEC) gave a judgement in Claydon Yield-O-Meter v Mzuri, a UK case on patent invalidity because of prior disclosure. As is known, in order for an invention to be considered new under Section 2(2) of the UK’s Patents Act 1977, it must not form part of ‘the state of the art’, i.e. all matter which is available to the public anywhere in the world in any manner, before the priority date.

It should be reminded that even if there is no one to observe the disclosure, just a possibility of prior public use being observed can rob an invention of its novelty. This principle was previously affirmed in Lux Traffic Controls Ltd v Pike Signals Ltd (1993). In that case, the invention related to a traffic signal light system. Before the filing date, field trials had been carried out by the applicant. The defendant argued that the invention had been made available to the public because a prototype had been used in public and it did not matter whether anyone observed the particular feature claimed by the patentee. It was held that the relevant claim of the patent was invalid for lack of novelty. Indeed, the court noted, a prototype was made available to a contractor and – if a skilled man had examined it – he/she would have seen how it worked. Whether such person examined it did not matter. To back up this argument the court pointed out that a book on the library shelf may be deemed a prior disclosure even if no one has actually ever opened and read it.

Background and decision in Claydon Yield-O-Meter v Mzuri

Claydon Yield-O-Meter Limited (‘Claydon’) was the claimant. Mzuri Limited (‘Mzuri’) and Christopher Martin Lole (sole director of Mzuri) were the defendants. The two companies are both manufacturers and sellers of agricultural equipment. Mr Jeffrey Claydon, CEO of Claydon, to whom the patents were granted, appeared as a third party to the dispute. Claydon filed a case against Mzuri claiming infringement of both its UK and European patents. The patents protected a seed drill, which is attached to tractors for precisely sowing seeds. The inventor, Mr Claydon, tested the invention prototype in his farm for ten hours over two days, before filing for the patents. There was a six-feet tall hedge surrounding the farm and the hedge had several gaps from where anyone could peep into the field. Mzuri contended that Claydon’s prototype could have been seen by anyone from the footpath to which the public had access, providing enough information to enable an understanding of the invention.

Muzri therefore filed a counterclaim for revocation of both the UK and European patents for lack of novelty due to public prior use. Mr Claydon declared that due to his prior experience of patents, he knew prior public disclosure of his invention could threaten his ability to patent it. He further explained that such experience made him take necessary measures; from the vantage point of his tractor cab, he could see anyone in the vicinity before they could even have a chance to glance at the field so if he had seen anyone, he would have moved away, making the drill prototype not visible to anyone.

The Court held Claydon’s patent invalid because of prior public disclosure. Judge Hacon distinguished E. Mishan & Sons Inc. v. Hozelock, where it was held that a series of tests of the patented hosepipe by the inventor in his garden did not amount to prior public disclosure, as the inventor was well aware of the danger. Indeed, if the inventor had become aware of someone watching him, he would have taken the hosepipe somewhere else where it would be out of sight to everyone. As mentioned, Judge Hacon distinguished such case and found that even if the inventor had been aware of someone passing by, he would not have been able to conceal it due to the (big) size of the seed drill.

Practical and legal issues

This decision raises the practical question how inventors can confidentially test and develop large inventions outdoor at their own premises. One may note that the bigger the machinery which incorporates the invention, the more difficult it is to test and develop the technology in question.

Also, decisions like Claydon Yield-O-Meter v Mzuri may be detrimental to specific industries (such as agricultural machinery) where innovation processes require large scale experiments involving big products. One may even go as far as claiming that this would contravene the principle of non-discrimination based on the field of technology under Article 27 TRIPS, which states that patents shall be available and patent rights enjoyable without discrimination as to field of technology. In other words, inventions incorporated in bigger products might de facto be discriminated vis-a’-vis inventions related to smaller ones.

The concept of de facto discrimination was clarified by a 2000 WTO Panel’s report in Canada – Patent Protection of Pharmaceutical Products (para 7.101):

  • “[D]e facto discrimination is a general term describing the legal conclusion that an ostensibly neutral measure transgresses a non-discrimination norm because its actual effect is to impose differentially disadvantageous consequences on certain parties, and because those differential effects are found to be wrong or unjustifiable”.

It seems to us that this fits into the Claydon Yield-O-Meter v Mzuri scenario. Judge Hacon’s finding in the ruling looks neutral as it is not formally addressed to a particular category of inventors or fields of technology. Yet, its actual effect is to impose negative consequences on inventors within industries which require large scale tests: a finding which is therefore difficult to justify and consider fair.


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  1. There is so much wrong with this decision, I hardly know where to start. Pity it will very likely not go to appeal. I always thought that English style fact-finding, built around cross-examination of witnesses, was superior to anything in the civil law world, and thereby is a gift to the world because it keeps the parties “honest” when litigating the same issue in civil law jurisdictions. But here, the fact-finding was (in my eyes) so lamentable, it screwed the whole case, on the law.

    I think the judge had no choice, but if the witness evidence had been of higher quality, the judge could have reached the right result in a much less controversial way.

    Perhaps it is because this case was on the “cheap and cheerful” litigation path of England, the “Enterprise” court. Perhaps EPO-style fact-finding works better in a poor man’s court? In a no expenses spared, High Court action, perhaps the witness examination might have been of higher quality.

    Interesting is the difference between witness “preparation” for x-exam, in the UK and in the USA. In England, such “preparation” is beyond the pale, and therefore often fatal, but in the USA it is fatal NOT to do it, and very thoroughly. Here, in this case, a modicum of “preparation” might have contributed to getting to the right result. My guess is that it is not just me but also the witnesses that were left disappointed.

    I should say that I grew up on a farm. My quarrel with the evidence concerning the “disclosure” in the field is that, from a distance, an observer (even an expert) would not have been able to distinguish the machine being trialled from the machine illustrated in the EPO’s starting point prior art, an old US patent on a seed drill. The only difference from the prior art was the relative positions of two delivery pipes, respectively for seeds and fertilizer, near the points of the respective alternate tines, underground when the drill is working.

    So the notional observer, peering through the hedge a hundred yards away, would not have been able to say whether the machine on trial was an embodiment of the prior art, or something somehow different from the long-known machine. The distinguishing feature of the claim in suit is discernable only upon close inspection, inches away from the machine.

    See the parallel EPO opposition proceedings, for how this case should have been decided.

    While I lament a sad day for fact-finding, England-style, I leave others, more learned than me, to say whether, on the facts derived from the witness testimony, the judge got the law right.

  2. I would have thought that what is disclosed in such a situation is merely the outline of the machinery and not how it is actually built up and how its different internal elements cooperate.
    Following this logic, when a large piece of machinery is exposed in the courtyard of a manufacturer, and the door is open or the fence is not a closed one, then the whole machine was made publicly available.
    This cannot be true.
    Another example is when a test car of manufacturer is driving through the streets, does it mean that any device used in this test car has been made available to the public? it is a good joke, no more.
    It is to be hoped that the court of appeal and, should necessity arises, the UKSC will bring an end to this very artificial way of looking at a disclosure.
    If the test equipment is sold or made available to third parties without a confidentiality agreement, then I can accept the reasoning.
    With due respect, is the judge having drafted this decision sitting in an ivory tower?

    1. Attentive, your thoughts prompt some of my own.

      There is a parallel case at the EPO, that went through the opposition process. Instructive is the contrast between the EPO way of finding the facts and that of a court in England.

      I think that, here, the judge had little choice in the matter, given the precedents and the outcome in his court of the cross-examination of the witnesses.

      The way i see it, the claimed subject matter differs from the prior art starting point, if at all, then by a small difference of the relative positions of the seed and ferlilizer delivery tube ends and the relative positions of the respective tine tips. I seriously doubt that even an expert with binoculars could tell, from the other side of the hedge, whether the machine working in the field was an embodiment of the prior art or the claimed invention. One needs to be “up close and dirty” to tell the difference, inches away, rather than half a furlong away.

      For this reason alone, the prior “public” use attack should have failed.

      But if the barrister doesn’t prove it, by skillful x-exam of the witnesses, then the judge lacks crucial material on which to base his decision.

      What do other readers say

    2. Well, according to IPkat writing on this in April, all of the claimed features would have been visible from the path…

      If this is true, then it might actually have been a public disclosure. From the articles here and in IPkat it is not possible for me to form an opinion on this, as the details are not clear to me.

      The article here is somewhat over the top, I think: in the few cases where an invention is so clearly fully visible from the outside, it should be possible to file an application first.

      I am wondering, how the other party knew about the tests and their location… Discovery?

      1. Fragender, yes indeed, From the IPKat write up:

        “On the basis of expert witness testimony, the Judge also concluded that a hypothetical skilled person would have been able to deduce all of the claimed features of the invention from their vantage point at the edge of the field (para. 101). ”

        But why not form your own opinion? Compare the drawings of the patent GB-B-2400296 with those of the prior art Handy US 5161472. Imagine an EPO-style 2-part form of claim. See how little there is in the characterizing part, and how it concerns the exact relative position of the (below ground) seed nozzles and fertilizer nozzles. If you can discern that characterizing feature from behind a hedge a hundred yards away from the moving machine working in the field you’re a better man than I am, Gunga Din.

        HHJ Hacon writes about the skilled person being able to “deduce” the feature. I suppose he alludes to obviousness, for wouldn’t it need to be “directly and unambiguously derivable” to attain the Gold Standard and so have any hope of prejudicing novelty?

        In the USA, they routinely resort to the eligibility criterion as a short cut to knock out obvious subject matter. I think it would be a shame here if the novelty provision is used as a short cut to avoid using the obviousness provision to knock out a bad claim.

        1. MaxDrei, I actually looked at the patent and the decision, though not in great detail.

          I am reluctant here, because I do not have real experience in farming equipment design…

          My first impression is that claim 8 of the patent does not have many features, and they are quite general, so yes, the person skilled in the art would probably have “seen” all features of the claim in the field. Regarding claim 16 I have some doubts. But then again, I do not have the technical background needed here, nor an overview of typical prior art seed drills…

  3. Fragender, I’m grateful for your reminder about the IPKat item in April. I see that it attracted a sizeable thread of comments too. If Kluwer would be so kind as to release this post to the thread, below is a Link to the IPKat posting


    The way I see it, there are two interesting aspects to this case, one about the law of prior “public” disclosure and the other about the way the facts are established, in litigation in England. On that issue, Fragender, you ask an interesting question: how did the Other Side find out about the field trials.

    I suspect that the answer is that the lawyers acting for Claydon, being “officers of the court”, have a professional duty to tell the Other Side about the trials. But, hey, I don’t litigate cases in England. Other readers who do might want to add their 6 penny-worth in answer to Fragender’s point. Then perhaps this Blog can pick up the discussion where the IPKat left off?

  4. @MaxDrei Yes, it seems an interesting case.

    The questions raised seem very case specific, to me. And it reinforces, why members of ODs hate any opposition where a public prior use is alleged – IMHO it’s much more difficult to decide on witness testimony than assessing documents. So every examiner I know will do a really thorough search, if this comes up in an opposition…

  5. The case reminds me of an alleged public prior use at the EPO when the opponent claimed that he could see from a bridge the connection between two vehicles which were passing underneath.
    The BA calculated that at the speed of the vehicles on the track he could have seen the connection for a fraction of a second only. That the vehicles passed 32 times did not change the facts.
    The PPU was, rightly, dismissed!

  6. Thank you, Attentive and Fragender. So, dear readers, what might we take from all this?

    In England, choose your witnesses carefully, because coaching them is strictly forbidden. Brief your advocates intensively so that they ask the witnesses the right questions, under cross-examination.

    At the EPO, presenting a case to the OD or the TBA, you are addressing three persons skilled in the art, so show them the evidence that really does demonstrate, to a standard “more likely than not”, that there really was a PPU. The Board, hampered by the Gold Standard, will run a mile rather than write a Decision striking down the patent on a PPU but will surely then make extra-zealous efforts to knock the claim out using Art 56, EPC.

    At the EPO there is no Binding Precedent, so the Board has far more freedom than a judge in England, to write a creative Decision that ends up with the “right” result.

  7. I would not say that “members of ODs hate any opposition where a public prior use is alleged”. In some situations it is the only prior art available and they have to deal with it. It is clear that should there be other means to come to a decision, that is patent or non-patent literature, an OD will prefer it.

    The problem with witnesses is that they can only confirm what has been said in the opposition statement and what they know first-hand.
    Any information from hearsay is dismissed, so it is no so often that a witness’ statement is really conclusive.

    The opposition might be admissible but not well founded.
    Not to forget that the when, why and how have to be on file within the opposition period. Otherwise the opposition will be rejected as well!

  8. Attentive, indeed!

    As to fact-finding as practised by the Boards of Appeal at the EPO, I wonder whether you have yet seen T1872/17. Oral proceedings in person 26 April 2021 in which a member of the Board drew lines on the back of his hand with samples helpfully brought along to the oral proceedings by the Applicant, samples offered to the Chair with an assurance that they were indeed the ones used in certain comparative tests reported by Applicant.

    From observation of the back of his hand, the Board member was able to confirm that, to his surprise, one particular sample exhibited “a slightly increased fading tendency” relative to another sample. For him, this was sufficient to evidence the presence of an inventive step despite the ED’s refusal of the application.

    Perhaps Applicants who draft patent applications that tell tales of achievement of surprising and unexpected technical effects can enhance their prospects of grant by arranging personal face to face interviews with Examiners at the EPO, and bring with them material evidence of the surprising and unexpected technical effects of which they tell in their patent applications.

    Or, in the case of agricultural seed drills, make videos and show them to the tribunal. I wonder whether it occurred to Claydon to make such a video and show it to the judge in the English court. Proving a negative is hard, but such a video might have helped the judge to the idea that seeing the detail of the tine tip configuration from behind that distant hedge was a somewhat dubious proposition. To say the least.

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