The Boulton Paul Defiant was designed in response to Air Ministry Specification F9/35 of 26 June 1935 calling for a two-seat fighter with all its armament concentrated in a turret. It was believed at the time that, in avoiding an enemy aircraft’s slipstream, fire from a powered turret would be more accurate than that provided by fixed forward firing guns. Five companies responded to the specification but, for various reasons, four withdrew leaving Boulton Paul the sole contender.
Designed by John Dudley North, the P82 prototype (minus turret) first flew on 11 Dec 1937 at which point it was named the Defiant. A second prototype was fitted with a Type A four-gun turret based on a French design already licensed for use on Boulton Paul’s Overstrand bomber, and this version with but minor changes became the production Defiant Mk1. The turret was electro-hydraulically operated with a mechanical backup and carried 4 x .303 Browning machine guns, electrically fired with cut-off points in the turret ring preventing activation when pointing at the propeller disc or tailplane. Whilst the gunner could lock the turret forward and transfer firing control to the pilot, this was rarely practised given forward elevation restrictions and the lack of pilot gunsight.
The Defiant entered RAF service with No 264 Squadron in December 1939 and saw combat for the first time in May 1940 during the evacuation of Dunkirk. It was initially successful with Luftwaffe fighters sustaining losses, but a change of enemy tactics with attacks from below or head on soon saw Defiants forfeit the initiative. Following the loss by 264 Squadron of 7 aircraft with 9 crewmen dead over the three days 26th to 28th August 1940, the Defiant was withdrawn from the day fighter role. Four squadrons were equipped with the aircraft for night fighter duties, however, and it is apposite that during the “Blitz” of 1940-41 the Defiant destroyed more enemy bombers than any other type. It was finally retired from the front line in 1942 and thereafter used for training, target-towing, ECM and air sea rescue – many aircraft having had their turrets removed. The “Daffy”, as the Defiant was affectionately known, also saw service with the Royal Navy and the air forces of Australia, Canada and Poland.
A total of 1,064 machines were built. A single survivor is on display at the RAF Museum, and it is understood that the Medway Aircraft Preservation Society is restoring a second. The aircraft was a regular visitor to RAF Tangmere during the early 1940s and it is reported that on one such visit in April 1941, Defiants of No 264 Squadron operating from the station shot down a He111 off Beachy Head.