Abstract: Power actuated dead-locking unit for a centrally controlled vehicle door locking system has a lock actuating formation (20) which is shifted between locked and unlocked positions by a motor driven rotary operating cam (16), the latter holding the actuating formation in a dead-locked condition at a first position and allowing free movement of the formation between locked and unlocked conditions at a second position to which it is resiliently urged. A motor driven dead-locking catch (28) is movable between an engaged position at which it coacts with a formation (26) of the operating cam with the latter at its first position for dead-locking without having to keep the motor driving the operating cam continuously energized, and a disengaged position leaving the operating cam free.