In 1816 printing engineer Edward Cowper of London received British patent No. 3974 for "A Method of Printing Paper for Paper Hanging, and other Purposes."
"Cowper . . . recognized, like Nicholson, the advantages of a curved printing surface mounted on a continously revolving cylinder. The difficulty was to provide this surface. Cowper, who would have been aware of the Bacon and Donkin project, must have realized that single types, however shaped or arranged, had very serious disadvantages, and that the solid stereotype plate offered much better prospects of success if they could be curved.
"The only method of casting stereotypes known at that time was the plaster process, which produced a flat plate. Cowper's patent described how these plates were to be heated and then passed between two rollers to curve them. There was, of course, the risk of breaking the plates during the operation, but the method worked; it was used for printing £1 notes at the Bank of England, where these machines were installed for the purpose" (Printing and the Mind of Man. Catalogue of the Exhibitions and the British Museum and Earl's Court 16-27 July 1963  No. 408).