It was the pilot's normal practice to commence descent to the circuit area at a point 10 kilometres from the strip. On this occasion the descent was initiated 4 kilometres from the strip and the aircraft was some distance past the strip when the pilot was ready to conduct the downwind checks. During the checks he elected to leave the landing gear up until the final approach checks. Had the landing gear been extended at the normal point in the check sequence, the pilot expected that he would have to apply extra engine power which he did not wish to do . Shortly after starting the final checks he was distracted by a radio call from another aircraft. He responded to the call and then restarted the final checks, but in the wrong order. The aircraft landed with the flaps fully down and the landing gear retracted. The pilot reported that he did not hear the warning horn.