V8914 was lost in a crash on April 7, 1940, only two weeks into its flight test program. The cause was aileron flutter. The wreckage was left on the bottom of the Firth of Clyde as a war grave to the three crew killed in the accident. While the concept of a retractable hull was considered proven, the project was cancelled. The idea was revived in September 1941 then cancelled again two months later. Photo from: Air Force Museum of New Zealand

It seemed like a good idea - improving the aerodynamics of seaplanes by using a large central float or pontoon that could be retracted to conform with the fuselage. Built at the Blackburn seaplane factory in Dumbarton, the B-20 prototype V8914 first flew on 26 March 1940 but crashed on 7 April, probably due to aileron flutter. The project was then given up, although the concept had shown promise and was kept secret, making the B-20 one of the least-known British aircraft of the war. Photo from: Air Ministry (UK)