The patent was for a test that applied that principle. The integers of claim 1 were for (a) use in scintillation proximity test (b) of a phosphor (c) that has an emission maximum of 480nm-900nm, (d) and of a charge coupled device (e) for detecting radiation emitted by the phosphor.
"When some of that radioisotope becomes bound next to the surface carrying the phosphor, the radioactivity emitted by the radioisotope causes the phosphor to be excited and emit light. The amount of light produced is proportional to the quantity of radioisotope bound to the surface and can be measured by a scintillation counter. The radioactivity emitted by the radioisotope which remains in solution is absorbed by the fluid. In this way, bound radioisotope gives rise to a scintillation signal but unbound radioisotope does not, and this has the benefit that there is no need to separate the one from the other as is the case with conventional radioimmunoassays. For this reason, SPAs are known as homogeneous assays as opposed to heterogeneous assays, which involve a separation step."
The action was for infringement of the above claim plus two other claims of the patent. The defences were anticipation, obviousness and obtaining. There was no dispute that if the patent had been valid it would have been infringed but the judge held the patent to be invalid for obviousness.
The judge took as his starting point Aldous LJ's discussion of "common general knowledge" in Beloit Technologies Inc v Valmet Paper Machinery Inc  EWCA Civ 993 (12 Feb, 1997) - a case in which he had appeared as counsel. He also reminded himself of Mr Justice Laddie's observation in Raychem Corp.'s Patents  RPC 31 at 40 that general knowledge is not limited to material which the skilled person has memorized and has at the front of his mind but also includes all that material in the field in which he is working which he knows exists, which he would refer to as a matter of course, if he cannot remember it, and which he understands is generally regarded as sufficiently reliable to use as a foundation for further work.
Reminding himself that particular care must be taken to avoid hindsight reasoning when considering an argument that an invention is obvious in the light of common general knowledge, the judge analysed the prior art and concluded that each of the claims in issue were invalid for obviousness.