D Napier & Son produced a range of piston driven aero-engines. Interstingly, and unlike other major British aero engine manufacturers, every Napier engine type was of a different design.
Like the other large manufacturers Napier's pursued Air Ministry contracts designing engines to suit their requirements. For example, after the hugely successful Lion engine Napier's next design was the Cub, the first 1,000 HP aero engine. It was designed for a Ministry requirement for a single engined bomber. The problem with this design was the Ministry changed its mind and decided that it was safer to have multi-engined bombers! So the design failed!
Follow the links above to read about Napier's piston aero engines.