Whilst returning from the training area after a period of dual instruction, the engine suddenly stopped. Engine failure cockpit checks, which reportedly included selecting the alternate fuel tank, failed to restore power. The pilot declared an emergency and turned the aircraft toward a racecourse, the only available area for a forced landing. The aircraft touched down safely but the nose landing gear leg failed due to the action of heavy braking on soft earth. Subsequent investigation determined there was no fuel in the right fuel tank, although the left tank contained about 48 litres. The engine started and ran normally when the left tank was selected. The instructor pilot had failed to adequately monitor the rate of fuel usage from the right tank during the flight and the engine consequently stopped due to fuel exhaustion.