Patents: obviousness and common general knowledge

By Audrey Horton


The High Court has held that a patent for smart utility meters was obvious, and proposed amendments would not be allowed as they added matter, but if the patent had been valid, it would have been infringed.


A patent is invalid for lack of inventive step if the invention claimed was obvious to a person skilled in the art having regard to the state of the art at the priority date (section 3, Patents Act 1977). The Court of Appeal set out a structured approach to the assessment of obviousness in Windsurfing International Inc v Tabur Marine (Great Britain) Ltd ([1985] RPC 59).


M was the exclusive licensee of a patent for smart utility meters.

B commenced proceedings in the Intellectual Property Enterprise Court for revocation of the patent for invalidity.

M issued a claim for infringement in the High Court against B, together with an application to transfer B's invalidity proceedings to the High Court. B's invalidity proceedings were transferred to the High Court and both proceedings were consolidated. B and M were ordered to produce amended statements of case, to include a statement of case as to the essentiality of the patent, setting out its alleged relevance to the UK Department of Energy's Smart Metering Implementation Programme. Essentiality and any other relief would be determined at a separate hearing.


The court held that the patent was invalid as being obvious over the prior art and that the requested amendment was not allowable. It also held that if the patent had been valid, B would have infringed it.

The court rejected M’s argument that B should be limited to the validity case pleaded in its statement of case. The case had to be determined by reference to the evidence given at the trial. Statements of case were to assist the parties in the preparation of their cases, but they could not be used to preclude the court from deciding the case on the evidence actually given.

However, greater caution was required if the case advanced of alleged obviousness over common general knowledge alone had not been pleaded in the statement of case. Arguments based on common general knowledge alone were more susceptible to hindsight by ignoring inconvenient features of actual prior art references and needed to be treated with care. Where a party was relying on obviousness over common general knowledge alone, it should set out in its statement of case not only what the common general knowledge was alleged to be, but also how that differed from the invention of the patent and why this rendered the claim obvious. That required a pleading not of just the starting point, but of the allegedly obvious route to the claimed invention so that the notional thinking of the skilled person could be seen and evaluated.

Usually, a case of obviousness over common general knowledge would be set out in a statement of case before expert reports and the case might reasonably develop from them on the evidence. Inconsistency during a case of the argument as to why a patent was obvious over common general knowledge might sometimes shed light on whether the argument was sound and whether it was really obvious, but the mere fact that this argument had developed in the light of the way that the patentee developed its case, as here, gave this inconsistency limited weight.

The court rejected M's argument that the invention was the idea of using a neutral identifier for the purpose of opening up a pre-payment meter to wireless access unconstrained by suppliers. This was not justified by the specification or the claims of the patent. It seemed to be a reconstruction, using hindsight, of an allegedly more specific inventive concept that was not contained in the patent itself.  

In determining whether an alleged invention would have been obvious, the court had to assume that the skilled person had common sense. This approach ensured that patents were not granted for the application of common sense to technical problems, even though the prior art did not specifically say that a particular technique ought to be used and it was not possible to point to specific direction to do so from the common general knowledge.

The court rejected B's defence of experimental use. While trials for mixed commercial and research purposes may still be experimental, here the purpose of the trials was not directly related to the patent's claimed subject matter.


This decision is a warning to patentees that, just as those attacking their patent cannot use hindsight, they are not permitted to use hindsight to construct a defence of their patent from a general statement in the description that was not claimed nor clearly described in the specification. 

The decision also highlights the difficulties of preparing a statement of case at a relatively early stage of revocation proceedings. Careful consideration should be given as to whether it is possible to base an obviousness case on common general knowledge alone, given the requirement that the statement of case should, in addition to specifying the common general knowledge relied on, show the route by which the invention could be reached from this information by the skilled person.

Interestingly, a meter which could nowadays be operated as a pre-payment meter by installing software, rather than one hard-programmed to act as such, could still infringe the patent, even if that facility was s not activated. However, the court noted damages or injunctive relief might not be available where meters were installed with that capability but the facility was not activated.

Case: Meter-Tech LLC & Another v British Gas Trading Ltd [2016] EWHC 2278 (Pat).

First published in the November issue of PLC Magazine and reproduced with the kind permission of the publishers. Subscription enquiries 020 7202 1200.