The Firefly was designed by a team led by H.E. Chaplin at Fairey Aviation which reportedly used the Fulmar as a starting point. During June 1940, the Admiralty placed an initial order for 200 aircraft "off the drawing board", the first three of which were to function as prototypes. On 22 December 1941, the first prototype of the Firefly performed its maiden flight. Although the aircraft was heavier than the preceding Fulmar (largely due to the adoption of the heavier Griffon engine and the armament of two Hispano cannon in each wing), the Firefly was faster due to improved aerodynamics, as well as the increased power of the Griffon IIB engine, being capable of generating a maximum of .