The primary armament of the Tribal-class destroyers was eight quick-firing (QF) 4.7-inch (120 mm) Mark XII guns in four superfiring twin-gun mounts, one pair each fore and aft of the superstructure, designated 'A', 'B', 'X', and 'Y' from front to rear. The mounts had a maximum elevation of 40°. For anti-aircraft (AA) defence, they carried a single quadruple mount for the QF two-pounder Mk II "pom-pom" gun and two quadruple mounts for the 0.5-inch (12.7 mm) Mark III machine gun. Low-angle fire for the main guns was controlled by the director-control tower (DCT) on the bridge roof that fed data acquired by it and the rangefinder on the Mk II Rangefinder/Director directly aft of the DCT to an analogue mechanical computer, the Mk I Admiralty Fire Control Clock. Anti-aircraft fire for the main guns was controlled by the Rangefinder/Director which sent data to the mechanical Fuze Keeping Clock.