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Obviousness before the UK Court of Appeal

Date: 16 December 2020

For those fortunate to have gardens, the English spring and summer of 2020 were hot and glorious. As soon as COVID lockdown ended, folks flocked to the DIY stores. Gardening products were in high demand. Winter had been wet, so there was no hosepipe ban as there had been in 2018. Hoses were selling well, including a new self-expanding type of garden hose.

A self-expanding hose is one that, when not in use, shrinks to a compact size for storage but expands under normal mains water pressure to many times its at-rest length.



Emson, Inc (E. Mischan & Sons) are a US company who sell innovative products through catalogues, TV sales and retailers. Emson offered a patented self-expanding garden hose under the brand “XHose”, but, a leading UK hose manufacturer, Hozelock, entered the market and Emson sued for patent infringement.

It was a brave move on the part of Hozelock, because Emson had previously asserted their patent against another infringer, Tristar. Emson sued Tristar just 3 months after the patent was granted, and the patent was held to be valid and infringed. That was in 2013. Tristar appealed. The validity of the patent was upheld by the Court of Appeal.

This second time around, Hozelock defended based on the same prior art as had been relied on by Tristar, and having lost before the Patents Court, Hozelock also appealed. Brave indeed. Hozelock were asking the Court of Appeal to come to a different conclusion based on the same prior art. The only difference would be the expert evidence. Hozelock thought they had presented a better case than Tristar.

The prior art relied upon was somewhat obscure. Expert evidence was critical. The Court of Appeal were faced with a tricky case.


Not res judicata


In another jurisdiction, it might not be possible to re-litigate the validity of a patent based on the same prior art documents. Not so in the Courts of England and Wales. Indeed, the Court of Appeal noted “the previous decisions are not admissible evidence on any question of fact arising in the present case.” The function of the judge was to decide this case on the evidence adduced by parties in this case. Indeed, the expert testimony in this case was materially different to that in the previous case.


“Obscure” prior art

The somewhat obscure prior art reference (“McDonald”) was not a garden water hose. It was not even a water hose. It was an oxygen mask for cabin crew of an aircraft. It worked in the same way as the invention, although it had a number of shortcomings in its description that left many questions as to whether a skilled person might find its teaching applicable to a garden hose.




It is well established law that where there is prior art, however obscure, which discloses the same invention, then patent protection is unavailable. If it were otherwise, novelty would depend on the circumstances and even language of publication of the prior art. But is the same true for obviousness?


The approach to obviousness in the UK is well established and is known as the four-step “Pozzoli” approach. This case more-or-less hinged on the first step.


The four-step Pozzoli approach to obviousness in the UK:

    1. Identify the person skilled in the art, and then identify the relevant common general knowledge of that person.
    2. Identify the inventive concept of the claim in question.
    3. Identify what, if any, differences exist between the matter cited as prior art and the inventive concept of the claim.
    4. Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention?


The Court accepted that the relevant skilled person was interested in design and manufacture of garden hoses and would typically have exposure to both garden and “technical hoses” used for commercial use.
The expert for Hozelock had been employed since 1994 in design and manufacture of garden hoses and technical hoses. His evidence was that the operation of the prior art hose of McDonald did not depend on the type of fluid (oxygen versus water), and a skilled person “would immediately see” that it could be used for other hoses including a garden watering hose. The Court accepted this proposition.


This was in contrast to the conclusion in the previous case. In that case, the Court held that the relevant skilled person was a garden water hose designer. The judge in that case (Mr Justice Birss) wrote


“I think a garden water hose designer presented with McDonald... would see a document which was not addressed to him or her... used in an environment and context a very long way from garden water hoses and subject to considerations which the garden water hose designer would know they knew little about.” 


It may be noted, however that Birss J. rejected the proposition that McDonald should not even to be put before a person skilled in the art at all for the purposes of testing obviousness. He said I believe that is not the law. His conclusions were upheld by the Court of Appeal.



In the later case against Hozelock, Lord Justice Floyd gave a dissenting opinion. He said “viewed against the common general knowledge of garden hoses, the invention was one of breathtaking ingenuity bringing with it real, practical advantages.”

He agreed that there is no support for the proposition that “the state of the art” can be different for novelty & obviousness, but he said that the policy behind denying protection for something that is obvious vis-à-vis an obscure document “loses its force when the evidence shows that a skilled person would not even have looked for such a document.”


McDonald was a “mere paper proposal” (quoting Ferag AG v Muler Martini [2007] EWCA Civ 15). He said it was not right to assume that a paper proposal could be successfully implemented. The shortcomings in McDonald (see inset box) that the majority had dismissed one-by-one were “not irrelevant in this regard”.


Alleged shortcomings in the description of McDonald

  1. McDonald did not disclose the hose diameter - evidence was adduced as to typical oxygen hose diameters (narrow) and garden hose diameters (thicker) but also some evidence of overlap; anyway, the teaching was not tied to any diameter.
  2. Materials unfamiliar to a garden hose designer – but the skilled person is familiar with different materials for different hoses.
  3. McDonald does not disclose the gas pressure - not an issue to the judge - all the skilled person needs to know is that there is sufficient pressure to cause the tube to self-elongate. The person skilled in the art is not reading McDonald to consider how good it is as an oxygen mask; only to address problems of space, weight and kinking in a garden hose.
  4. No disclosure of how to initiate flow of oxygen - again, the expert in oxygen masks probably knows this and the designer of garden hoses doesn’t care.
  5. No disclosure of how the hose retracted itself - doesn’t matter, it’s enough that it says that it does retract.

The lack of detail is not such that the skilled person would put McDonald aside as being altogether too confusing.



So it all came down to whether the person skilled in the art was a garden water hose designer or was a designer of hoses more generally, including hoses for a wider range of technical purposes.

In the earlier trial, the defendants (Tristar) called a witness who was a polymer materials engineer experienced in the properties, design and durability of polymer materials and products. In the later case, the Defendants (Hozelock) called the CEO of a sister company, Tricoflex, that supplied Hozelock with its garden hoses but also sold a range of technical hoses for gases, fuels, oils, chemicals, food and water among other things. He was an “impressive witness” having worked on the development of garden hoses but also, as he progressed through the company, on technical hoses.

There was no disagreement between the various judges that the obscure prior art should be put before the notional skilled person. This is the approach taken by the European Patent Office in identifying the “closest prior art”. It is a question not of whether the skilled person trying to make a better hose would come across the document in his or her search – rather it is a question of a skilled person who happens to be reading that document asking the question “how can I modify this to solve an objective problem?” In this case the problem might have been formulated along the lines of adapting the McDonald hose to use it for other purposes, such as water. But one might still question whether it is fair (or an application of hindsight) that such a person is skilled in the design of garden hoses and is not, for example, an aircraft engineer. The UK courts approach a given document in a very similar way. The notional skilled person is deemed to read any given piece or prior art with interest. Having done so, the skilled person is fully entitled to say (quoting from Asahi Medical v Macopharma): “I have read it with interest, but I am not interested.” This was not such a case. The majority decided that the prior art document was within the field of the skilled person, would have been of interest and would not have been dismissed as a bad idea.

Bringing the right expert witness to court is key in many cases of obviousness. The UK courts love an expert. A good expert can be very damaging to validity of a patent. For an example of a battle of the experts, in which a Professor from the University of Sheffield played a trump hand for a patentee, see L'Oreal v RN Ventures [2018] EWHC 173


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