[2][3] Westland proceeded to independently develop the Sea King, integrating a significant proportion of components from British suppliers; key changes include the use of a pair of Rolls-Royce Gnome turboshaft engines and the implementation of an automatic flight control system.

[8] The first of the SH-3Ds was initially fitted with General Electric T58s and, after being shipped from the United States, was flown in October 1966 from the dockside at Avonmouth to Yeovil airfield.

[8] The first two helicopters were used for trials and evaluation by Westland and the Aeroplane and Armament Experimental Establishment; subsequent production Sea Kings were delivered to the Royal Navy's 700 Naval Air Squadron from August 1969 onwards.

First flying on 26 September 1979, due to its operational range of up to 600 nautical miles without refuelling, the HC4 'Commando' became an important asset for amphibious warfare and troop transport duties, in particular.

Initial trials carried out with active Sea Kings found several advantages to the BERP rotor, including a longer fatigue life and improved aerodynamic characteristics.

The Sea King Airborne Surveillance and Control (ASaC) variant is expected to be replaced around the introduction of the two Queen Elizabeth-class aircraft carriers.

[21] A 16th helicopter was ordered shortly after, and following the Falklands War of 1982, three more were purchased to enable operation of a SAR flight in the islands, initially from Navy Point on the north side of Stanley harbour, and later from RAF Mount Pleasant.

[23] On SAR variants, the cabin was enlarged by a stretch of the fuselage behind the door; another key feature, used for additional flotation in the unusual event of a water landing, inflatable buoyancy bags were housed inside the aircraft's sponsons.

[24] Upgrades and changes made to SAR Sea Kings include the addition of radar warning receivers, a cargo hook for the underslung carriage of goods, and the redesigning of the cockpit for compatibility with night vision goggles.

[26] The Royal Navy's airborne early warning (AEW) capability had been lost when the Fairey Gannet aeroplane was withdrawn after the last of the RN's fleet carriers was decommissioned in 1978.

Consequently, two Sea King HAS2s were modified in 1982 with the addition of the Thorn-EMI ARI 5980/3 Searchwater LAST radar attached to the fuselage on a swivel arm and protected by an inflatable dome.

These prototypes, designated HAS2(AEW), were both flying within 11 weeks and deployed with 824 "D" Flight on HMS Illustrious, serving in the Falklands after the cessation of hostilities.

The main role of the Sea King ASaC7 is detection of low-flying attack aircraft; it also provides interception/attack control and over-the-horizon targeting for surface-launched weapon systems.

[33] In the theatre, they performed a wide range of missions, from anti-submarine patrols and reconnaissance flights to replenishment operations and the insertion of special forces.

[35] Sea Kings also protected the fleet by acting as decoys against incoming Exocet missiles, with some missions being flown by Prince Andrew, Duke of York.

[37] On 14 June, an 820 NAS Sea King HAS.5 was used to transport Major General Jeremy Moore to Port Stanley to accept the surrender of Argentine troops on the island.

[37] A Flight of 824 Naval Air Squadron embarked two Sea King HAS.2As aboard RFA Olmeda and were used to move supplies to other ships on the way south and later anti-submarine patrols.

[40] From the departure of Hermes from Ascension in April until the Argentine surrender, the squadron operated at least three helicopters airborne continuously for fleet protection.

[40] On 23 April 1982, a Sea King HC4 was ditched while performing a risky transfer of supplies to a ship at night, operating from the flagship HMS Hermes.

[44] During the 1991 Gulf War Sea Kings from several nations, including Canada, Britain, and the U.S., were present in the coalition forces against Saddam Hussein's Iraq regime.

[45] Due to the threat of potential use of any Iraqi weapons of mass destruction, it was standard practice for Sea King crews to wear fully enclosed NBC (nuclear, biological, chemical) protective suits.

[46] Britain's Sea Kings primarily engaged in inter-ship transport duties, including ferrying troops between the fleet and land.

[49] Following the end of hostilities, the available Sea Kings remained on deployment in the region to conduct transport missions to relocate people displaced by the conflict to refugee camps and repatriate citizens to their home countries.

On 22 March 2003, two AEW Sea Kings from 849 NAS operating from Ark Royal collided over the Persian Gulf, resulting in the death of seven personnel.

[66] During the 2003 Iraq War, Sea Kings were heavily used in logistical roles, such as the first delivery of humanitarian aid to the Iraqi capital, Baghdad.

[71] The farewell flight was conducted on 15 December 2011, three Sea Kings flew over Sydney Harbour and across to Canberra, passing Lake Burley Griffin and the Australian War Memorial before landing at Nowra.

[78][82] In 1982, India signed a contract to purchase several Mk42B Sea Kings, an upgraded variant to perform dual-purpose: anti-shipping and anti-submarine missions, following a competition for the order against the Aérospatiale Super Puma.

[86] Although the Indian Navy considered the AEW Sea King, expected to be designated as Mk42D, it was judged to be too expensive, consequently, in 2003, the Russian Kamov Ka-31 was procured instead.

[91] In the late 2000s, HAL and AgustaWestland signed an agreement to jointly maintain and perform upgrades to India's fleet of Sea Kings.

The German Navy placed an order for 22 Sea King Mk.41s on 20 June 1969 as a replacement for the Grumman Albatross flying boat in the Search and Rescue Role.