The battle against the kamikazes in World War II demonstrated the need for the earliest possible early warning of attack. The solution was to raise the search radars high enough to expand the “horizon” around the task force, which was achieved after the war by creating airborne early warning. The first aircrfaft t o carry a search radar was the Douglas Skyraider. During the mid to late 1950s, the Royal Navy operated detachments of Skyraider AEW.4 aircraft from its carriers.

The Skyraider was obviously approaching obsolescence at the time it was adopted, while the need for a more modern AEW aircraft became more pressing. The Royal Navy issued AEW.154 to initiate planning for a Skyraider replacement. The most-suitable aircraft were those under development in the GR.17/45 specification for a new anti-submarine aircraft. The Fairey Type Q/17 was declared the winner and entered service as the Gannet.

A decision was made to use the Gannet as a stop-gap measure prior to the development of a new, purpose-built aircraft for use on the planned new generation of aircraft carriers. The Skyraider’s AN/APS-20 radar would be mounted under the fuselage.

However, the radome’s size meant the Gannet airframe would have to be modified since it was too close to the ground to accommodate the radar. The fuselage was radically changed, with the removal of the two observer’s cockpits and the creation of a new compartment within the fuselage at the trailing edge of the wing. This meant the turboprop exhausts had to be moved forward from this position to the wing leading edge. The additional area of the radome created directional instability, which required a larger vertical fin and rudder to compensate. Finally, the landing gear needed to be to increase clearance for the radome.

The extensive modifications led to a suggestion that the AEW version be renamed the Albatross, given it was to all intents and purposes a completely different aircraft. However, by the time the Gannet AEW began entering service in the early 1960s, the ASW Gannet was in the process of being replaced.

The Gannet AEW.3 prototype first flew in August 1958; carrier trials were held aboard HMS Centaur in November, and the first production aircraft was delivered in December. 700G Naval Air Squadron was formed in August 1959 as the Trials Unit for the new aircraft; the intensive test program lasted until January 1960, at which point the unit became 'A' Flight of 849 Naval Air Squadron and was embarked aboard HMS Ark Royal. A total 44 Gannet AEW.3s were delivered by 1966.

The Gannet AEW.3 had limited command and control capability, since it had no onboard computer(unlike the contemporary E-2B Hawkeye) and used the AN/APS-20 S-Band search radar and AN/APX-7 IFF set, connected to the AN/ART-28 Bellhop datalink, which transmitted information to the operations room on the aircraft carrier, where intercept directions were given to the CAP.

The Gannet’s three-man crew consisted of the pilot and two observers in the fuselage compartment. The aircraft had a typical endurance of 5–6 hours at 25,000. The airplane cruised on one engine of the Double Mamba, alternating between the engines every 30 minutes.

849 NAS operated the AEW.3s in four operational flights plus the HQ flight. The HQ flight was stationed at three Fleet Air Arm air stations over the period of Gannet operation. Each flight operated four AEW.3s and a Gannet COD.4 for ship-to-shore communications. Five Royal Navy carriers operated the Gannet AEW flights.

The British government’s decision in the mid-1960s to cancel the planned new carriers led to the withdrawal of fixed wing aviation in the Royal Navy. C Flight was disbanded following the withdrawal of HMS Centaur; A Flight was disbanded in 1970 when Hermes was withdrawn; D Flight disbanded in 1972 when Eagle was decommissioned. The final operational AEW.3s were operated by 'B' Flight aboard HMS Ark Royal until her final decommissioning in 1978 – a Gannet AEW.3 XL471 of 849B Flight was the last aircraft to land on the ship on Saturday 18 November 1978.

849 Naval Air Squadron was disbanded in December 1978 following the decommissioning of Ark Royal, wich left the RN with no emb edded airborne early warning. The RAF took over Airborne Early Warning for the UK Air Defence Region, with the radars originally supplied with the Skyraiders taken from the Gannets and fitted to the obsolete Avro Shackletons. The lack of organic AEW capability for the navy following the withdrawal of the Gannet was seen as misguided, particularly following the experience of the Falklands War, where four ships were lost due to the Task Force being reliant on shipborne air search.