The Mk II was the only version of the Lancaster not to be powered by Rolls Royce Merlin engines. Instead, it used Bristol Hercules radial air cooled engines. The aim was to provide an alternative source of Lancasters in case the supply of Merlin engines failed. British production was seen as vulnerable to German bombing, while there were worries that American production (by Packard) would be diverted or stopped if American entered the war.
Work on the prototype Mk II began soon after the Mk I was complete, and the first prototype flew on 26 November 1941. The new model was produced by Armstrong Whitworth, with work beginning in March 1942. Ironically, while Rolls Royce was free from serious attack, the Armstrong Whitworth factory was itself bombed in June 1942, delaying the appearance of the Mk II.
Paint Scheme 1 - Avro Lancaster BII 'Z-Zombie', No.408 (Goose) Squadron, 6 Group, Royal Canadian Air Force, Royal Air Force Linton-On-Ouse, Yorkshire, July 1944.
Paint Scheme 2 - Avro Lancaster BII 'Fanny Ferkin II' No.514 Squadron, 3 Group, Royal Air Force Waterbeach, Cambridgeshire, November 1944.