Designed to Air Ministry Specification 27/24, which called for a single-seat night fighter for use against enemy bomber aircraft, the Bittern design was unusual for its time in that it was a twin-engined shoulder wing monoplane rather than a single-engine biplane.

The first prototype had two fixed .303 in (7.7 mm) Vickers machine guns mounted on the fuselage sides.

These could be angled from 0-45° upwards so the fighter could attack bombers from below without having to put the aircraft into a climb.

[1] Both were finished in dark green with "night black" undersides for their role as "Anti-Bomber Formation Fighters".

The first prototype carried out full performance and armament trials at Martlesham Heath from March 1927; the second went through the same tests in April 1928.