The Boulton Paul P.103 was a design for a naval fighter based on the Defiant turret fighter.
Although few of Boulton Paul's own designs reached production, the company produced a large number of other aircraft during the Second World War, amongst them the Barracuda. This gave them some expertise in the construction of naval aircraft, and their chief designer, John North, put some thought into the ideal performance for a carrier based aircraft.
Early in 1943 Specification N.7/43 was issued, calling for a single seat fighter based on an existing design. The original specification called for a radial engine, but with an inline engine allowed as an alternative. Under pressure from Boulton Paul the specification was then changed to allow for a design study of an aircraft powered by the Rolls Royce Griffon engine. The design had to be ready by 24 April 1943.
Boulton Paul submitted two designs in response to N.7/43. The P.103 was based on the Boulton Paul Defiant, but with more powerful engines - either the Griffon RG5SM (P.103A) or the Centaurus CE12SM (P.103B). This was perhaps a poor decision, as by 1943 the Defiant had been seen as a failure for several years. The P.103 was to have an all-round vision bubble canopy, wings that folded in two steps, first by revolving by 90 degrees and then swinging back against the side of the aircraft. Rocket assisted take off was possible.
Boulton Paul's second design was the P.104, one of several tail first pusher designs produced by Boulton Paul.
Neither of the Boulton Paul designs was selected. Instead in May 1943 the Naval Staff went with a lightweight version of the Hawker Tempest, which would become the Hawker Sea Fury. Boulton Paul did much of the work on navalising the Fury design.
Some features from the P.103 and P.104 were considered to be worthy of further examination, and a contract was issued for the construction of a 'Special Features' Defiant, which would have had the Griffon engine, contra-rotating 'dive break' propellers and an undercarriage with legs that extended when lowered, to allow for the large propellers (an alternative to the inverted gull wing used on other designs). This aircraft was never built.