Martin Howe QC acted for the defendant in successfully resisting an application to revoke a patent relating to a process for moulding plastic articles with a sandwich type construction of solid plastic outer surfaces and a foamable plastic core. HHJ Birss QC held that a process step involving the use of a former to make the side walls was not obvious in the light of the prior art, and that amendments made to the claims of the patent did not result in the addition of matter. Accordingly the defendant was permitted to amend the claim in the manner it sought and the claim as amended was valid.