Such a large glider had never been constructed before by the British military, and to test the design, a half-scale prototype model was first designed; designated GAL. 50 it still required an Armstrong Whitworth Whitley medium bomber to act as a tug to get it airborne, and was first flown in September 1941. However, it only flew once; the test pilot approached the landing area too low, attempted to raise the flaps for extra glide, and instead crashed the prototype and wrecked it. However, the trial was considered to be a success and the first full-scale prototype model was finished at GAL's works in Hanworth, Middlesex in March 1942. The Hamilcar was transported to RAF Snaith in Yorkshire, as GAL's airfield at Hanworth was too short for the glider to take off from; moving the glider to a secure military airfield would also ensure that it remained secret. Its first flight was conducted on 27 March 1942, towed by a Handley Page Halifax bomber. A second prototype was completed in June 1942, and further testing and development took place at a number of different airfields, including the Airborne Forces Experimental Establishment at RAF Beaulieu; all flight trials appear to have been successful, and there were few differences between the prototypes and the production models.