The pilot was in the process of purchasing the "Cygnet" and had flown to Forest Hill to fly the aircraft before the purchase was finalised. On the day before the accident, he completed several flights in the "Cygnet", the last of which resulted in a forced landing after the engine failed. On the day of the accident the pilot planned to return to his home, but the aircraft he had flown to Forest Hill was unserviceable and departure was delayed until the following day. That afternoon when the "Cygnet" had been repaired he made another successful flight in the aircraft, which was also subsequently flown by another pilot. At 1505 hours, the pilot again took-off in the "Cygnet", for a ten minute flight. During this flight several flypasts were made along the strip before an approach to land was made. Witnesses report that the approach was misjudged and after touchdown the aircraft bounced several times before the pilot applied power and carried out a go-around. The aircraft then climbed straight ahead with full power set before making a steeply banked turn onto the crosswind leg of the circuit. A flat tight turn through 180 degrees was then made and the aircraft appeared to witnesses to be flying very slowly. During the turn one witness reported that the pilot's left foot came off the rudder pedal and control was partially lost. After control was regained, the aircraft continued flying slowly, it was seen to oscillate in pitch several times before the left wing dropped and it entered a spin. No change in engine noise was noticed during the spin and the engine continued to operate until the aircraft impacted the ground. Inspection of the aircraft did not reveal any pre-existing fault that would have contributed to the accident. It was subsequently found that the pilot was a diabetic and at the time of the accident he was markedly hypoglycaemic. The erratic way in which the aircraft was flown prior to impact indicates that the pilot lost control of the aircraft due to his being incapacitated as a result of hypoglycaemia.