The pilot decided to divert to a nearby aerodrome because the fuel gauges indicated a low fuel quantity remaining. Shortly after commencing the diversion the engine failed. During the ensuing forced landing the aircraft struck a fence post, overturned, and slid inverted for 120 metres. The engine had failed from fuel exhaustion. During the flight, which involved 3 landings, one refuelling and about 6 hours flight time, the pilot had not conducted a check of the aircraft fuel consumption. Although the fuel gauges indicated a higher than normal rate of consumption, the pilot did not land at suitable enroute aerodromes and the diversion was not made until a critical situation had developed. Subsequent examination of the engine and fuel system did not establish the cause of the excessive fuel consumption.