In 1941, Supermarine and the designers of the Spitfire explored a new Rolls Royce engine, the Griffon, as an alternative powerplant that the Spitfire might be able to grow into. The Spitfire XIV was the definitive Griffon Spitfire and it did that with a two stage supercharger, longer nose, enlarged vertical stabilizer, and several other refinements to the design, with 150 octane fuel enhancing low altitude performance putting the XIV within a hair of the other high speed late war fighters.