In the Summer of 1941, a pre-production Beaufighter Mk.I was selected as one of the platforms for evaluating the use of the new 40 mm cannons. Two designs were in consideration, the Vickers S and Rolls-Royce BH. To test these cannons, a Beaufighter Mk.I prototype was modified to have the new cannons installed in place of its usual 20 mm autocannons. Also, all suspended and even defensive armament was removed from the aircraft. The results of the test went on to select the Vickers S 40 mm cannon for follow up development.

Introduced as a reward for Battle Pass: Season V, "River Hunter", the Beaufighter Mk I (40 mm) presents strong firepower for use against air and ground targets. Although this Beaufighter does not carry any suspended ordnance, the 40 mm armed Beaufighter presents enough penetrating power to threaten the weaker armour on tanks. The large calibre explosive power would also allow the Beaufighter to decimate large fighters and bombers. That said, the availability of only large cannons means this plane would not do well against manoeuvrable small fighters.