The Bristol Type 135 cabin monoplane, designed by Frank Barnwell in 1933, attracted the attention of the Press baron Lord Rothermere, who in 1934 ordered a Mercury-engined version for his own use as part of a campaign to popularise commercial aviation. The aircraft first flew in April 1935 and soon caused great interest in Air Ministry circles on account of its high performance its top speed of 307 m p h being higher than that of any R.A.F fighter in service. Lord Rothermere generously presented the aircraft (named "Britain First") to the nation for evaluation as a bomber and in early 1936 the modified design was designated Blenheim Mk.I
The type was ordered "off the drawing board", and first deliveries to No 114 Squadron began in March 1937. By the time of the Munich crisis sixteen home-based bomber squadrons were equipped with the type. When war broke out in September 1939 seven home-based fighter squadrons had re-equipped or were re-equipping with the Blenheim IF, a fighter version with four extra 303 in. Brownings in a belly pack. As a day fighter the Blenheim IF was a failure, proving to be fairly easy meat for single-engine interceptors, and casualties were high. Like the Defiant, it served as a useful night fighter where its roomy fuselage and comparatively high loiter capability could be utilised to the full in this role.
Powerplant: Two 840 hp Bristol Mercury VIII nine-cylinder air-cooled engines.
Span: 56ft 4in (17.14m)
Length: 39ft 9in (12.11m)
Max Speed:285 mph (460km/h) at 15,000 ft (4,572m)
Armament: Four .303in Browning machine guns mounted in a ventral fairing, one .303in machine gun in hydraulically-operated semi-retractable dorsal turret.
Accommodation: Pilot and air gunner.
Recognition: Sleek, pointed nose with large glazed area for the cockpit which is almost hidden by the wing-mounted engines when viewed from the side. Small air gunner's position on the upper fuselage. Main undercarriage retracts into engine fairings part-way along the mainplane.
Bristol Blenheim 3-angle view.