 The DH.93 Don was intended to be a trainer for pilots and radio operators, and as a gunnery trainer, the gunnery requirement involved the mounting of a dorsal gun turret.Student pilot and instructor sat side by side up front, while accommodation for a trainee WT (radio) operator and the turret gunner was behind in the cabin.The prototype with test marks "E-3" (later military serial number "L2387") first flew on 18 June 1937 and was transferred to RAF Martlesham Heath for official evaluation.