The first F4Fs to enter British service did so as a side effect of the collapse of France. Well aware that their re-armament plans would not be ready in time, the French ordered 81 Grumman G-36As, the export version of the aircraft. This was powered by the Wright R-1820-G205A Cyclone engine, a similar radial engine to that used in the F4F-3 but with a single-stage supercharger. It was armed with two 7.5 mm machine guns in the engine cowling and another in each wing. The first of these plans flew on 10 May 1940. On the same day the German invasion of France began. In the time it took Germany to conquer France, Grumman only built seven G-36As.
With the collapse of France, Britain took over as many French orders as possible. Amongst them were the 81 Grumman fighters. Modified to British standards, they arrived in Britain late in 1940. The most significant modification was to the guns – the French 7.5mm guns were replaced by four .50 calibre (12.7mm) machine guns, two in each wing, just as in the standard F4F-3. On 25 December 1940 two Martlets of No. 804 Squadron shot down a Junkers Ju 88 bomber near Scapa Flow, the first American built aircraft to score a victory in British service. The fixed wing Martlet I was not used as a carrier aircraft, instead operating with land based Fleet Air Arm squadrons.
The next set of Martlets were ordered by Britain after the collapse of France. The Martlet II used the same Wright R-1830-90 engine as the F4F-3A, with a single stage two-speed supercharger. One hundred were ordered. The first nine Martlet II’s arrived in March 1941, with fixed wings and four guns. However, the rest of the order was modified to include the new six-gun folding wing used on the F4F-4. The Martlet II was used on carriers, seeing action in the Mediterranean in 1941-3, including during Operation Torch, and also during the invasion of Madagascar.
The thirty Martlet IIIs also entered British hands after the collapse of an ally, this time Greece. They had been ordered as F4F-3As, with the same engine as the Martlet II but non-folding wings and four guns, as the Martlet I. The aircraft were en route to Greece when the country fell in April 1941, and were diverted to British hands in North Africa. There they operated with the Fleet Air Arm, but from land bases.
The Martlet IV (also known as F4F-4B) was a product of Lend-Lease. Two hundred and twenty Martlet IVs were delivered between February and November 1942. They were powered by the Wright R-1820-40B Cyclone engine, again with a single-stage two-speed supercharger. The Martlet IV shared the same six-gun wings as the F4F-4.
At the start of 1944 the British adopted the American names for their Marlets, but kept the original mark numbers (so the Martlet IV become the Wildcat IV). The Wildcat V was the General Motors produced FM-1. The Royal Navy received 311 Wildcat Vs.
Finally, the British received 340 FM-2 Wildcats, under the designation Wildcat VI.