My favourite Merlin story relates to wartime outsourcing, when Ford was asked to produce the engines at Dagenham. RR is said to have been rather condescending when Ford came back with queries on dimensions and tolerances which they said were not tight enough for Ford production methods. If they produced 10,000 spare parts, as they often did, each one had to fit every car that left the production line as perfectly as the original.
Ford went on to produce 20,000 Merlin engines, and not one failed its acceptance tests.