Bristol Type 173 Mk1,2 & Mk3 – 2x 755/1 Mk 155, 780 hp, 755/2 Mk 160, 780 hp or 2x 850 hp Handley Page Herald – four 870 hp on Prototype Handley Page H.P.R.1 Marathon – four Westland Whirlwind 1 x 755/1 Mk 155, 780 hp