A lock mechanism for locking together first and second relatively moveable components (50 and 51), which mechanism comprises: - a lock body for attaching to the first component; - a bolt assembly for attaching to the second component so as to be opposed to the lock body as the two components come together, the bolt assembly carrying at least one ball which is moveable outwardly relative to an outer surface of the bolt assembly to project therefrom; - an opening (15,31) defined by the lock body for receiving the bolt assembly, the opening having an internal groove for receiving the at least one ball of the bolt assembly when projecting therefrom; and - an operating pin carried by the lock body and being received in a bore in the bolt assembly when said two components come together so as to move the at least one ball radially outwardly into the groove in the lock body thereby locking together the lock body and bolt assembly; characterised in that: - the bolt assembly includes a locking member which is resiliently biased to a normal position but is moveable away therefrom against the resilient bias, the locking member being provided with the at least one ball moveable outwardly relative to the outer surface of the locking member to project therefrom; - the operating pin is resiliently biased to a rest position but is moveable axially away from its rest position; and - there is provided an operating mechanism (26, 27, 20) for driving the operating pin axially away from its rest position so as to move at least partially out of the bore in the locking member when received therein, thereby allowing the at least one ball to move out of the groove in the lock body and so unlock the lock mechanism. - a lock body for attaching to the first component; - a bolt assembly for attaching to the second component so as to be opposed to the lock body as the two components come together, the bolt assembly carrying at least one ball which is moveable outwardly relative to an outer surface of the bolt assembly to project therefrom; - an opening (15,31) defined by the lock body for receiving the bolt assembly, the opening having an internal groove for receiving the at least one ball of the bolt assembly when projecting therefrom; and - an operating pin carried by the lock body and being received in a bore in the bolt assembly when said two components come together so as to move the at least one ball radially outwardly into the groove in the lock body thereby locking together the lock body and bolt assembly; - the bolt assembly includes a locking member which is resiliently biased to a normal position but is moveable away therefrom against the resilient bias, the locking member being provided with the at least one ball moveable outwardly relative to the outer surface of the locking member to project therefrom; - the operating pin is resiliently biased to a rest position but is moveable axially away from its rest position; and - there is provided an operating mechanism (26, 27, 20) for driving the operating pin axially away from its rest position so as to move at least partially out of the bore in the locking member when received therein, thereby allowing the at least one ball to move out of the groove in the lock body and so unlock the lock mechanism.