Whilst the aircraft was engaged in a circuit training flight, the engine suffered a loss of power on base leg. The instructor took control and carried out a forced landing. As the aircraft descended, power cables were spotted on the approach path and in avoiding them the aircraft landed short of the intended field and collided with a hedge. The aircraft was severely damaged in the collision. In the absence of any mechanical defects, carburettor icing is considered to be the most likely cause of the power loss, given the number of risk factors present on the day.