Beyond numerous improvements made to the Welland engine that powered the early Meteors, Rolls-Royce and Power Jets collaborated to develop the more capable Derwent engine, which as the Rover B.26 had undergone a radical re-design from the W.2B/500 while at Rover.
Ud over de talløse forbedringer af Welland motorerne der sad i de første Meteorer, indgik Rolls-Royce og Power Jets et samarbejde om at udvikle den langt mere kapable Derwent motor, som under navnet Rover B.26 havde været igennem et radikalt re-design af W.2B/500 mens den var i Rovers hænder.