Rolls-Royce Merlin prey, Rolls-Royce named the engine the "Merlin" after a small, Northern Hemisphere falcon ("Falco columbarius"). Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The Rolls-Royce Peregrine was an updated, supercharged development of their V-12 Kestrel design, while the 42-litre (2,560 cu in) Rolls-Royce Vulture used four Kestrel-sized cylinder blocks fitted to a single crankcase and driving a common crankshaft, forming an X-24 layout. This was to be used in larger aircraft such as the Avro Manchester. Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since
Rolls-Royce Crecy fighter. Studies on the de Havilland Mosquito also showed it to raise complex problems with Crecy installation. In 1942 Rolls-Royce Hucknall received a North American P-51 Mustang for engine installation trials. This prompted a series of studies for a Crecy version and the Mustang turned out a more suitable mount than the Spitfire. However these studies were not taken further. As the possibility of a flight-worthy engine approached, on 28 March 1943 Hawker Henley "L3385" was delivered to Hucknall for fitting with a Crecy. However the engine never became available and the aircraft remained at Hucknall until when it was