On arrival overhead at the destination aerodrome, the pilot elected to land into a strong headwind on the grass strip. The nose landing gear failed when the nose wheel dug into the grass surface during the application of heavy braking, and the aircraft overturned. Investigation revealed that the approach speed had been higher than optimum for the weight, and skid marks on the strip indicated that a series of heavy brake applications had been made during the landing roll. The nose landing gear was inspected, and it was found to have fractured in torsional overload. It is considered that the combined effects of the aircraft not being flown at the optimum approach speed, the heavy application of brakes on a grass strip and the failure of the pilot to adequately compensate for the resultant pitch down of the nose contributed to the accident.