10/31/2011. Remarks by Ray Watkins: "In 1934 the Air Ministry issued several specifications for fast and heavily-armed monoplane fighters to replace the obsolescent biplanes in service with the RAF.

Specifications F.9/35 and F.10/35, for one and two-seat day and night fighters respectively, led to the acquisition of the Boulton Paul Defiant turret figter against the former specification. Notably these two specifications called for an unprecedented armament of six, and preferably eight, 0.787 in (20 mm) cannon.

Considerable rethinking went on with F.10/35, in light of the success with the Hurricane and Spitfire, leading to its replacement with F.37/35 for a single seat, single-engined day and night fighter. The specification still called for 0.787 in (20 mm) or 0.906 in (23 mm) cannon, but with the number selected to give a 'two second burst destructive effect'.

The requirement for a single engine was later removed and tenders were requested from eight companies from which five responded: Boulton Paul, Bristol, Hawker, Supermarine and Westland, who offer their P.9 with a pair of Roll-Royce Peregrine engines. Westland was chosen as the sole supplier and received a contract on February 11, 1937 for two prototypes (s/n L6844, L6845)."

Read also the remarks on page 8260.