When the Hawker Hart bomber entered service in January 1930, it outperformed all other RAF aircraft in service and thus the decision was made to procure a two-seat fighter version for use until the Fury was ready. Two modified Harts were produced as prototypes for evaluation. Powered by the supercharged Rolls Royce Kestrel V12 engine, each was equipped with two synchronised forward firing .303in Vickers machine guns and had the rear cockpit modified to accommodate a .303in Lewis gun and observer/air gunner. These were known as Hart Fighters, as were a further batch of 6 machines. The name Demon was adopted in 1932 and full production began shortly thereafter. The aircraft entered RAF service with No 23 Squadron in April 1933 and eventually equipped seven regular and five auxiliary squadrons. As the sole other operator, the Royal Australian Air Force purchased 64 machines.
The Demon was not a particularly successful fighter. Such was its speed that the rear gunner experienced considerable difficulty manoeuvring his gun against the slipstream. From late 1936 a number of aircraft built by Boulton-Paul were provided with a hydraulically operated Frazer-Nash turret shield in the rear cockpit and many earlier aircraft were retrospectively modified to this standard. This initiative greatly improved the rear gunner’s accuracy, but badly affected the performance of the fixed guns whenever the turret was pointed abeam.
The aircraft remained in service until late 1938, at which its units were re-equipped with the Bleheim1F. It was obsolete by the time war broke out in 1939 but a few continued to serve as target tugs and communications aircraft. A total of 305 Demons were built with several surviving on static display in various museums around the world. The sole airworthy machine took to the air in June 2009 following an 18-year restoration; it is owned by Demon Displays Ltd and currently based at Old Warden with the Shuttleworth Collection.
No 1 Squadron, RAF Tangmere operated its own Demon as the unit “hack” in 1938/39.