Britain began the process of replacing its Vickers aircraft machine guns with a new Colt/Browning design in 1935, with its adoption of the Colt MG40. This was essentially John Browning's air cooled M1919 machine gun made smaller and lighter, with an increased rate of fire, and reversible feed direction. British adoption began with the purchase of 60 guns and a license for domestic production. This production took a few years to get rolling (by both the Vickers company and BSA), and in the meantime an addition 1600 examples were procured form Colt - including this example, dated 1937.

A few changes were made to the British pattern of the MG40. Most significantly, the clockwork was redesigned to run form an open bolt. This was deemed necessary because British cordite-loaded .303 ammunition was more sensitive to cookoff than American powders, and it would also detonate catastrophically upon cooking off. Unfortunately, this particular example has American ANM2 clockwork, so I can't demonstrate that change here. In addition, the British developed their own muzzle devices. The initial pattern suffered badly from powder fouling, and the replacement pattern consisted of the booster seen on this example plus an option separate flash hider cone. It was primarily the changes in muzzle devices that prompted the change of designation from Browning Mk I to Mki*, MKII, and ultimate MkII*. In total, more than half a million of these guns were made during World War Two, forming the primarily armament for the RAF (including Spitfires, Hurricanes, and Lancasters).