At a height of about 150 feet after a normal take-off, the aircraft commenced to roll slowly to the right. Corrective control inputs appeared to the pilot to have little or no effect and the aircraft continued to roll, with accompanying nose drop and yaw. The right wing tip struck the ground, followed by the landing gear. The gear was torn off and the aircraft overturned, coming to rest across a drainage ditch. No fault was subsequently found with the aircraft which might have contributed to the loss of control. There was no evidence of wind shear or any other atmospheric disturbance. The pilot reported that the engine power, attitude and airspeed had been such that a normal climb should have been achieved. The reason for the accident has not been determined.