A locking device for a leaf pivotally mounted in a frame, the leaf having a leading face, a trailing face, a bottom edge and side edges, and being pivotally moveable relative to the frame between an open position and a closed position, the locking device comprising at least a first cam rotatable between an unlocked condition and a locked condition, the plane of rotation of the cam being perpendicular to the plane of the leaf when in the closed position, wherein in the locked condition the cam is engageable with a cam engaging surface on the leaf or the frame, engagement of the cam with the cam engaging surface preventing the leaf from moving away from the closed position.