Rolls-Royce Merlin prey, Rolls-Royce named the engine the "Merlin" after a small, Northern Hemisphere falcon ("Falco columbarius"). Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The Rolls-Royce Peregrine was an updated, supercharged development of their V-12 Kestrel design, while the 42-litre (2,560 cu in) Rolls-Royce Vulture used four Kestrel-sized cylinder blocks fitted to a single crankcase and driving a common crankshaft, forming an X-24 layout. This was to be used in larger aircraft such as the Avro Manchester. Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since
Rolls-Royce Welland Minister of Aircraft Production and the Boards of Rover and Rolls-Royce, the Rover jet factory at Barnoldswick was exchanged for the Rolls-Royce Meteor tank engine factory in Nottingham. A handshake sealed the deal. Rover handed over a total of 32 W.2B/23 engines to Rolls-Royce as well as four "straight-through" W.2B/26 engines, developed by Rover's Adrian Lombard. The W.2B/23 became the RB.23 Welland and the W.2B/26 became the RB.26 Derwent. Adrian Lombard moved with the engines from Rover to Rolls-Royce. Stanley Hooker helped in the task of ironing out the remaining problems, and things soon improved. A flight-quality /23 was fitted