These ships were based on the preceding B class, but were enlarged to increase their endurance and to allow for the inclusion of a QF 3-inch 20 cwt anti-aircraft gun. This class introduced a director control tower for British destroyers. The 'C' class were unique in having a split bridge, with the compass platform and wheelhouse separated from the chartroom and director tower. This unusual layout was not repeated. As per Admiralty policy in alternating Two-Speed Destroyer Sweep (TSDS) minesweeping gear and ASDIC (sonar) capability between destroyer flotillas, the C class lacked ASDIC and were designed to carry only six depth charges. The D class were repeats of the C's, except that the TSDS was replaced by storage for up to 30 depth charges and ASDIC.