There is described a lock mechanism for fixing to a moveable member or frame for locking the moveable member in a closed position in the frame. The lock mechanism comprises a bolt member (10) moveable between a disengaged position and an engaged position for engagement with the frame or moveable member. A restraining mechanism is provided to engage and restrain the bolt member (10) when the bolt member (10) is in the disengaged position. Status detecting means is also provided for detecting when the moveable member is in a closed position in the frame, the status detecting means being coupled to the restraining mechanism to cause the restraining mechanism to release the restraint on the bolt member (10) when the closed position is detected. Electrical drive means (134) moveable between a closed position and an open position is provided to drive the bolt member (10) into the disengaged position and to hold the bolt member (10) in that disengaged position. Finally, bolt (10) biasing means is provided to urge the bolt member (10) into the engaged position and to hold the bolt member (10) in the engaged position when the electrical drive (134) means moves to the closed position and the restraining mechanism releases the restraint on the bolt member (10).