According to ShortFinals.org, in 1941, in Trafford Park, Manchester, Ford UK had two assembly plants where they were told to build Rolls-Royce Merlins – lots of them! At the time, this engine was in the vast majority of British fighters and bombers, including the two which had just won the Battle of Britain, the Supermarine Spitfire and the Hawker Hurricane.

In his book Not Much Of An Engineer, Rolls Royce supercharger designer Stanley Hooker states that Ford UK looked at the Merlin engine drawings and said “we can’t build an engine to those tolerances.” Hooker said loftily (his words) “I suppose the tolerances are too tight for you?” ” No, they are much too loose – we use much tighter tolerances for car engines so all the parts are truly interchangeable without any hand adjustment needed.”

Ford re-drew the blue-prints for the Merlin, making it more suitable for mass production, and by 1944, over 400 engines a week were flowing out of the plants.

The first Merlin engine developed 880hp but by the time the last mark of Merlin was produced the power output was 2030hp.

The Merlin engine was then enlarged still further and named the Griffon. Aircraft which were powered by the Merlin engine include the Lancaster, Spitfire, Halifax, Hurricane, Battle, Defiant, Whitley, Mosquito, Hornet, York, Lincoln and North American Mustang.