A security door lock with a hinged door and a locking assembly. The door jamb has a number of apertures formed in a bolt receiving side of the jamb to receive a corresponding number of door bolts extendable from an outer free edge of the door. The locking assembly has a barrier panel spaced from the jamb to define a narrow longitudinal slot is adapted to receive a door guard member extending normally from an internal surface of the door adjacent the outer free edge, and is reinforced by the barrier panel against lateral flexing or distortion. A handle mechanism controls the lateral movement of the closure and the retraction or extension of the locking bolts.