The Destroyer Frigate Rebuild Programme
From the early 1950s work began on rebuilding the old War Emergency Destroyers into modern ASW frigates with the latest design influences from Bikini and the latest ASW weaponry.
23 hulls were rebuilt to Type 15 standard which was the top-end design with one twin 4in, one twin Bofors, two twin Bidder ASW torpedoes, two Limbo and space for a Fairey Ultralight helicopter aft. Some early ships had twin Squid until Limbo was ready and others had eight single Bidder torpedo tubes amidships. They were in service until 1970-73.
18 hulls were rebuilt to Type 18 standard which was less expensive as structual alterations were less, armament was roughly the same except that one quad 21in torpedo tube mount was retained and it was used to fire Bidder and normal anti-ship torpedoes (but not Fancy). These too served until 1970-73.