The pilot reported that he had selected the landing gear down, and first stage of flap while on the downwind leg of the circuit, but did not confirm the gear position during the pre-landing check either by observing the gear down lights or a visual check of the gear position through the window. Full flap was selected on short final, and power reduced during the flare with the aircraft settling on the runway in a wheels up landing. An investigation failed to find any problems with the landing gear or its system, and the pilot subsequently admitted that he had forgotten to lower the gear. The gear unsafe warning horn did not activate as the pilot had used a considerable amount of engine power throughout the final approach. Witnesses reported that after the aircraft came to a stop the landing gear appeared to be partially extended, and the gear lever was in the down position. This gives the appearance that the pilot had realised his mistake too late, and attempted to extend the gear just prior to touchdown.