Don't forget the Hallibag and the Manchester were built to P13/36 and were supposed to be twin engine bombers powered by the RR Vulture. The Lanc obviously came about after the failure of the Manchester, the Halibag being changed to 4 engines at the design stage The Stirling was the only bomber built to the original 4 engined spec. A Centaurus powered Super Stirling was planned: Top speed over 300mph, 29,000 ft ceiling and bomb load in excess of 20,000lb. However it was decided to continue with current types and Shorts were told to cease work in mid 42.