Bristol Buckingham The Bristol Type 163 Buckingham was a British Second World War medium bomber for the Royal Air Force ( RAF ) . Overtaken by events , it was built in small numbers , and was used primarily for transport and liaison duties . Design and development . In early 1939 Bristol suggested a bomber variant of the Beaufighter with their Hercules engines . British policy at the time was for medium bombers to be provided from the US allowing British industry to concentrate on heavy bomber designs but a design was requested preferably based on an existing design which effectively meant working with the Beaufighter or Beaufort . Bristol worked on their design first as the Bristol Type 161 then the Type 162 Beaumont . Air Ministry specification B . 7 / 40 called for a medium bomber to replace the Blenheim . The specification stipulated a speed of at least 300 mph with a normal load of 1 , 000 lb of bombs and a turret armed with at least two machine guns of 0 . 50 inch calibre . Only one manufacturer tendered a full design , but it did not meet with approval . Bristol then brought their Type 162 to the Air Staff , which was fortunately well matched to B . 7 / 40 and which led to a request for a completed mock - up and then a contract for three prototypes in late 1940 . The Beaumont was based on the rear fuselage and tail of a Beaufighter with a new centre and front fuselage . The armament was a mid - upper turret with four machine guns , four more machine guns firing forward and two firing to the rear . Construction began in late 1940 , with a new Air Ministry Specification B . 2 / 41 to be written around it . However changes in the requirements - removing dive bombing and " direct army support " which incoming US bombers were expected to be capable of - and increasing the performance requirement to allow for the future meant the Beaumont would no longer suffice . The changes in performance ( requiring a bomb load of 4 , 000 lb , a speed of 360 mph and a range of 1 , 600 miles ) meant a redesign by Bristol to use the Bristol Centaurus engine . The Bristol redesign with a larger wing and the more powerful engines was the Type 163 Buckingham . It had gun installations in the nose , dorsal and ventral turrets . Generally conventional in appearance , one unusual feature was that the bomb - aimer / navigator was housed in a mid - fuselage ventral gondola , resembling those on the earlier German Heinkel He 111 H and American Boeing B - 17 C and - D in appearance . This was part of an attempt to give all the crew positions unobstructed views and access to each other ' s positions . The bomb bay could hold a single 4 , 000 lb , two 2 , 000 lb , four 1 , 000 lb or six 500 - lb bombs . The rear of the gondola had a hydraulically powered turret with two 0 . 303 Browning machine guns . The dorsal turret of Bristol ' s own design carried four Brownings . A further four fixed , forward - firing Brownings were controlled by the pilot . Following more changes specification B . 2 / 41 was subsequently replaced with B . P / 41 . The first flight took place on 4 February 1943 . During testing , the Buckingham exhibited poor stability which necessitated the enlargement of the twin tails , along with other modifications . Operational history . By the time the design entered production , the requirements had already changed , with attacks against German industry being covered by the US by day and by RAF Bomber Command ' s de Havilland Mosquito s by night . The Buckingham was not considered suitable for unescorted daytime use over Europe , and in January 1944 , it was decided that all Buckinghams would be sent overseas to replace Vickers Wellington s . Once the Buckingham ' s handling problems were revealed , it was realised that the Buckingham was of little use and the Buckingham bomber was therefore cancelled in August 1944 . However , in order to keep Bristol ' s workforce together for later production of the Brigand and the Hawker Tempest , a batch of 119 had to be built . Uses for the aircraft were sought and a conversion to a communications aircraft was devised . After the first 54 had been built as bombers , the remainder were converted for high - speed courier duties with RAF Transport Command . The gun installations were removed and four seats and windows fitted in the fuselage . The aircraft were designated Buckingham C . 1 . Despite its 300 mph ( 480 km / h ) speed and superior range to the Mosquito transports , with only room for four passengers , the Buckingham was rarely put to use . A total of 65 Buckingham bombers were unfinished on the production line and ended up re - built as the Buckmaster a trainer for the similar Brigand . Considered the " highest performance trainer in the RAF , " the Buckmaster continued to serve as a trainer until its eventual retirement in the mid - 1950s .