Editing Heavy fighter (section)

==United Kingdom==
[[File:Bristol Beaufighter Mk.IC 1944.jpg|thumb|[[Bristol Beaufighter]]]]

Before the war the British sought two types of twin-engined fighters,  with turret-mounted and nose-mounted (cannon) armament respectively. The former because it was expected to give greater opportunity for attack at higher speeds compared to the biplane era; the latter because of loss of accuracy expected with heavy weapons installed in wings. One example of an aircraft to meet the latter was the [[Gloster F.9/37]]; later development into a night-fighter was curtailed in 1941 so that Gloster's design team could concentrate on [[Gloster E.28/39|British jet fighter projects]]. The limitations of pure turret fighters (though the single engine [[Boulton Paul Defiant]] was successfully adapted as a nightfighter) and aerodynamics of multiple cannon installations in turrets (such as [[Boulton Paul P.92]]) curtailed introduction of designs into service.

Perhaps in the belief that "[[The bomber will always get through]]", Britain lagged behind in heavy fighter development.<ref name = Times >''Mr Baldwin on Aerial Warfare – A Fear For The Future''. ''[[The Times]]'' newspaper, 11 November 1932 p7 column B.</ref>{{failed verification|reason=Newspaper is dated before most of the British development period|date=January 2020}} Apart from the [[Westland Whirlwind (fighter)|Westland Whirlwind]] and the high-altitude [[Westland Welkin|Welkin]], both built only in modest numbers (the former due to lack of engines, the latter due to changed requirement), the [[Royal Air Force]]'s wartime twin-engined fighters were all adapted from contemporary light [[bomber]]s. During the German advance through [[Battle of France|Holland, Belgium and into France]], squadrons using [[Bristol Blenheim|Bristol Blenheim 1Fs]], fitted with a ventral gun pack and operating as long range fighters, suffered heavy losses, and were withdrawn from daylight operations.<ref>{{cite web |title=Bombardment of Waalhaven Airfield, 10 May 1940 |url=https://www.tracesofwar.com/articles/3649/Bombardment-of-Waalhaven-airfield-10-May-1940.htm |website=Traces of War |access-date=28 January 2025}}</ref> As the Battle of Britain commenced, some of these Blenheims were then equipped with radar, operating as night fighters.<ref>{{cite web |title=No.600 (City of London) Squadron |url=https://www.rafweb.org/Squadrons/Sqn600-604.htm |website=Air of Authority - A History of RAF Organisation |access-date=28 January 2025}}</ref>

More successful was the [[Bristol Beaufighter]], started in 1938 as an interim aircraft to cover for delays in introduction of a cannon-armed fighter (the Westland Whirlwind). The Beaufighter design reused major portions of the earlier [[Bristol Beaufort|Beaufort]] [[torpedo bomber]]. Armed with six .303 inch (7.7&nbsp;mm) machine guns, four 20&nbsp;mm cannon and rockets, bombs or torpedoes, the Beaufighter was potent in the anti-ship and ground attack role in the Pacific and Europe. With the addition of [[radar]], it was one of the [[Royal Air Force]]'s main night fighters. Similarly, the successful [[de Havilland Mosquito]] fast bomber was simultaneously adapted for both day and night fighter use. A parallel single-seat twin Merlin engine fighter the [[de Havilland Hornet]] entered service in the immediate post-war period and served until 1955.

When there appeared to be a threat from German high-altitude bombers, the [[Westland Welkin]] was developed. This was a twin engine design with wide wings ({{convert|70|ft|m|abbr=on}}) to be able to intercept at {{convert|45,000|ft|m|abbr=on}}. The threat never materialised and Welkins did not see combat service. A contemporary design the six cannon armed [[Vickers Type 432]], which itself descended from a requirement  for a fighter with 40mm cannon, got no further than the prototype.

Due to the different requirements for naval fighter aircraft, the British put into service some heavyweight single-engine fighters such as the [[Fairey Firefly]].