No-one can be trusted less than an American wrt to Merlin history. The Merlin was a successfull design (and build), so America takes the credit. Production: "112,000 in Britain and more than 37,000 under license in the U.S" Merlins were built in the USA to UK design and specification. Mustangs were ****e with US (Allison) engines until the RAF fitted them with UK built Merlins