The aircraft was landing on the grass Runway 26 at Compton Abbas when the accident occurred. The weather conditions were fine, with a light westerly wind. The pilot reported flying a normal approach with full flap, achieving a smooth touchdown about 100 m beyond the runway numbers. During the rollout the aircraft suddenly pitched nose-up, followed by three further pitch oscillations of reducing severity. The pilot described the motion as being as if the aircraft had encountered a bump and he thought that an unseen undulation, associated with a footpath that crosses the runway, may have contributed to the event.