A mortice lock is disclosed which has a lock casing which provides a first point of entrapment and a second point of entrapment, a latch bolt which can move between a latching position and an unlatching position, a handle for moving the latch bolt between the latching position and the un-latching position, a key cylinder, an operating assembly and a locking member. The operating assembly can move between a first position in which a deflectable portion of the operating assembly engages with the first point of entrapment and a second position in which the deflectable portion engages with the second point of entrapment. Only the key cylinder can move the operating assembly between the first position and the second position. The locking member (which is not a shoot bolt or part thereof) can move between a locking position in which a portion of the locking member engages with the latch bolt to prevent the latch bolt from moving into the un-latching position, and an unlocking position in which the latch bolt can move into the un-latching position. The locking member is operatively associated with the operating assembly such that moving the operating assembly into the first position moves the locking member into the unlocking position and moving the operating assembly into the second position moves the locking member into the locking position.