Representing an attempt to design the smallest and lightest practical airframe around the most powerful available engine suitable for fighter installation, the Hornbill was built to Specification 7/24 and flown in late summer 1925. Of mixed construction, with a duralumin-skinned steel tube forward fuselage and fabric-covered rear fuselage, wings and tail surfaces, the Hornbill was at first powered by an 826hp Rolls-Royce Condor III eight-cylinder water-cooled inline engine with twin radiators under the lower wing. In May 1926, it flew with a 698hp Condor IV and a single ventral radiator. It possessed an armament of one 7.7mm Vickers Mk 2 machine gun. The Hornbill was the fastest armed aircraft to have been tested by the RAF when it commenced service evaluation at Martlesham Heath in late 1925, but rate of climb and service ceiling were poor and some handling aspects unsatisfactory. No production order materialised.