The Invincible class has its origins in a sketch design for a 6,000-ton, guided-missile armed, helicopter carrying escort cruiser intended as a complement to the much larger CVA-01-class fleet aircraft carrier.

[10] The cancellation of CVA-01 in 1966 meant that the smaller cruiser would now have to provide the anti-submarine warfare (ASW) taskforce with command and control facilities.

[14] By now, the design was for a 19,000-ton "CAH"[10] (helicopter carrying heavy cruiser, styled after the US Navy hull classification symbols) with up to fourteen aircraft and a Sea Dart missile launcher on the bows.

The comparatively short 170-metre (560 ft) flight deck made even STOVL rolling take-offs marginal for launching fully laden Harriers.

As part of upgrades during the mid-1990s, all three ships had the Sea Dart removed, with the forecastle filled in to increase the size of the flight deck.

When the Iranian Navy could not commit to providing sufficient personnel for manning the vessels, the ship order was cancelled in 1976.

[18] In Australian service, the ship would have been named HMAS Australia, and would operate as a helicopter carrier until a later decision on the acquisition of Sea Harriers was made.

[19] Invincible's service during the Falklands War showed that the White Paper's suggested reductions were flawed and both nations withdrew from the deal in July 1982.

This was due to the fact that the originally envisioned mission for the ships was to provide the heart of ASW hunter-killer groups in the North Atlantic during a war against the Soviet Union.

The RAF Harriers proved to be a temporary aberration at the time, but a permanent addition to the usual air group was made due to lessons learned during the war: the Sea King AEW2A (airborne early warning) version.

Illustrious carried the first examples of the type when it was rushed south in the aftermath of the Falklands War to relieve Invincible of its guard duty around the islands.

Other improvements were made to the class during the 1980s and early 1990s, in particular to increase the ski-jump exit angle on Invincible and Illustrious to 12° to match Ark Royal.

The Sea Dart magazines were converted to increase air-to-surface weapons stowage, and new aircrew briefing facilities created under the extended flight deck, both to support the embarkation of RAF Harrier GR7s as a routine part of the air group.

Following the integration of the Harrier GR7, typical deployments included seven or eight of those aircraft, pushing the Merlin onto the carrier's accompanying Fort-class auxiliaries.

The principal weapon of the Invincible-class carriers then became the Harrier GR9 flown by two Fleet Air Arm and two RAF squadrons until they were retired in 2010.