Bristol Blenheim/Bolingbroke Mk IV [@ RAF Duxford]

In August 1935 the Air Ministry issued Specification B28/35, covering the conversion of the Bristol Type 142, a fast eight seat passenger aircraft developed as a private venture, to the bomber role under the designation Type 142M. Some major modifications were necessary, including raising the wing from the low to mid wing position to make room for an internal bomb bay, and widening the nose section to accommodate both pilot and observer/bomb aimer. Defensive armament comprised a single 7.7mm (0.303in) Lewis machine gun in a power-operated dorsal turret; the thinking was that the aircraft was fast enough to out-run any contemporary fighter. A Browning 7.7mm (0.303in) was also installed in the port wing leading edge and fired by the pilot.