The aircraft was on a flight from Cardiff/Wales to Paris with an intermediate landing at Bristol . When the landing gear was selected during the approach to Bristol, the left gear failed to extend. The aircraft returned to Cardiff where full engineering facilities were available and, after a flypast, the tower confirmed the left gear was retracted. As repeated attempts to lower the gear were unsuccessful, extra fuel was burnt off before commencing an approach to runway 31 with the left gear retracted. The aircraft made a smooth touchdown and continued along the runway before finally coming to rest on the grass turning 90ø to the left after leaving the runway approximately 1200 m from the threshold. Full emergency services were available, and quickly at the scene, and evacuation was successfully completed without injuries to occupants. There was no fire. Examination of the aircraft hydraulic system showed it to be serviceable, including the emergency system. The aircraft’s left wing was lifted by crane and the landing gear lowered by removing the uplock lug from the oleo leg. Ground locks were fitted and the aircraft towed to the hangar for further investigation. Inspection of the uplock mechanism showed that a bolt was missing from the operating linkage. The bolt is in part of the linkage which is common to both main and emergency hydraulic systems. The bolt was found in the wheel bay and it was seen that the threaded portion had broken off. Initial metallurgical opinion is that it had failed in fatigue.