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