Designed specifically around the Seaslug anti-aircraft missile system, the primary role of these ships was area air defence around the aircraft carrier task force in the nuclear-war environment.

the new County class would be destroyer-leaders for aircraft carrier task forces and when operating "East of Suez" also play a traditional cruiser flagship role with shore bombardment, and attacking enemy shipping.

[10] In 1955 the new First Sea Lord Louis Mountbatten specified the development of 4,800 ton Fast fleet escort design (DNC 7/959) with a Seaslug missile replacing a stern twin 3-inch anti-aircraft mounting,.

A detailed March 1957 study following the Suez Crisis and the 1957 Defence White Paper decided to increase the size of the new missile destroyers to that of light cruisers and include some cruiser features[13][14] The study opted for a 505 ft (154 m) long hull with a fit of 18 Seaslug and four nuclear warhead fitted Seaslug for extended range anti-aircraft, anti-missile and anti-ship.

The success included hits in the lethal zone of two piston-engine Fairey Firefly radio-controlled drones at 16 km (9.9 mi) flying at a speed of 315-375 mph.

[17][18] While the missile worked against level flying targets, the beam guidance system was dubious at range and in rough water and eight fixed stabilisers were added to the design of the County-class.

Against staff advice, a tight fitting, fixed side-hangar for the anti-submarine Westland Wessex helicopter was added on the insistence of the First Sea Lord.

Lord Mountbatten classified the County-class as guided missile destroyers to gain Treasury and political support[24] with cruisers discredited in the media[citation needed] as colonial relics, obsolete gunships like battleships.

Its missile capability had been overtaken by aircraft development by 1962–63, when HMS Devonshire and Hampshire entered service, but in the early and mid-1960s the modern lines of these guided-missile destroyers, with their traditional RN cruiser style and their impressive-looking missiles, enabled the overstretched Royal Navy to project sufficient power to close down the threat of a militant, left-leaning Indonesia to Malaysia and Borneo during the Indonesia-Malaysia confrontation.

Their wings and fins would be reattached before being moved into the aft sections of the handling spaces and eventually loaded onto the large twin launcher for firing.

Corresponding doubt whether major conventional war was still possible on the basis of the last 1954-5 HC speeches of Churchill[43][42] and Eisenhower, justified large cutbacks of British and American large ship, destroyer and carrier programmes[44] and the future role and relevance of the Royal Navy was "unclear"[45] moving the RN to more limited East of Suez task forces with gun and Seaslug- and Seacat-armed destroyers escorting medium British aircraft carriers with only a limited nuclear strike capacity against ships and cities equipped with Blackburn Buccaneer S.1 (and then the improved S.2) strike aircraft mainly aimed to deter regional powers such as Indonesia.

[46] Early versions of the equivalent US missile system RIM-2 Terrier, like Seaslug, relied on beam riding and needed a nuclear warhead variant to compensate for inaccuracy at low level and range.

[47] The Royal Air Force's semi-active land-based Bristol Bloodhound was unrelated to Seaslug development, but drew top scientists away from RN work.

Although superior the Type 984 radar was rejected as it was even heavier and would excluded fitting a twin turret 4.5-inch armament forward which was needed for gunfire support or action against surface vessels.

Following problems with the original version, a reworked Action Data Automation Weapon System (ADAWS) was successfully trialled on HMS Norfolk in 1970.

[54] In the mid-1960s the County-class destroyers were assets; their impressive appearance and data links, feeding off the carriers' Type 984 radar, projected effective capability during the Indonesia–Malaysia confrontation.

[59] The second batch of four ships (Antrim, Fife, Glamorgan and Norfolk) were refitted in the mid-1970s – their 'B' turrets were removed and replaced by four single MM38 Exocet surface-to-surface anti-ship-missile launcher boxes in order to increase the fleets anti-ship capability following retirement of its aircraft carriers.

[20][page needed] Certainly, these arrangements as originally installed to operate a single Westland Wessex anti-submarine helicopter were problematic, with a hangar so cramped it took an hour to get the aircraft either in or out again, during which the port Seacat launcher was unusable.

However it was determined that beam-restrictions would still limit the Counties' helicopter operation in RN service to the obsolescent Wessex, as they were too narrow to handle the far more capable British-built Sea King HAS.

Glamorgan and Antrim are the counties in Wales and Northern Ireland which contain the port cities and regional capitals of Cardiff and Belfast (by analogy to London, England).

Her helicopter, a Westland Wessex HAS Mk 3 (nicknamed "Humphrey") was responsible for the rescue of 16 Special Air Service operators from Fortuna Glacier and the subsequent detection and disabling of the Argentinian submarine Santa Fe.

Glamorgan, after many days on the "gun line" bombarding Port Stanley airfield, was hit by an Exocet launched from land at the end of the conflict.

Her Navigating Officer's prompt reaction to visual detection of the Exocet narrowly averted a hit on the fatally vulnerable Seaslug magazine, by turning the ship so as to give as small a target as possible (the stern) to the incoming weapon.