Staff Writer (Updated: 4/4/2016):
The Beaufighter was originally proposed directly by Bristol to the RAF as a heavy fighter offering during a time when much focus fell to twin-engined, heavily-armed, long endurance gun platforms that could also serve in a limited ground strike role. While there was no formal need or specification drawn up for the new aircraft, it proved promising enough for the RAF to shore up its limited air arm. The RAF believed that the new fighter could favorably complement the existing stock of single-engine types and twin-engine medium bombers quite well. Due to the British commitment to World War, the need for any capable aircraft was great and the Beaufighter quickly joined RAF ranks. First flying on July 17th, 1939, the aircraft was introduced on July 27th, 1940 - some twelve months after the first prototype flew - a rarity for newly-developed war machines even by 1930s / 1940s standards. Serial production was underway in May of 1940 and would last until after the war in 1946. Since the new Beaufighter utilized many components of the existing Bristol Beaufort torpedo bomber (detailed elsewhere on this site), the implementation of the Beaufighter into RAF service was relatively quick and painless.
Due to its Beaufort origins, the "Beaufighter" name was formed from the words "Beaufort" and "Fighter".
The twin-engine heavy fighter featured a crew of two and was initially outfitted with an impressive armament array of 4 x 20mm Hispano cannons found under the nose and 6 x 7.7mm machine guns mounted in the wings. This armament was quite a powerful installation when compared to many other fighters of the war. The streamlined fuselage carried the cockpit, avionics, and other mission critical components while being set between the radial piston engines - these fitted to the leading edges of the wings and driving three-bladed propellers. The tail unit was highly conventional with a single rudder and low-set horizontal planes in play.
Beaufighters were delivered in time for September 1940 though most lacked their intended machine gun wing armament. Nevertheless, the four-cannon arrangement was sufficient enough to tackle any enemy bomber of the day and could serve double-duty in the ground attack strafing role. By the end of the year, more and more Beaufighters were finally seeing their full armament suite installed. The radar equipment, at the heart of any night-fighter, was developed at the same time as the aircraft and managed to be introduced at roughly the same time.