When I was at university we had a guest lecturer who was quite elderly and had seen life at Rolls Royce from Merlins to the RB211 and beyond. A 'proper' engineer with a cardigan, a pipe and glasses with thick black frames, on more than one occasion He said that that when they were sent the drawings for the Merlin, Packard replied that that they couldn't make an engine like that. Puffed up at their superior engineering, RR asked why not. The reply from Packard was that the tolerances were far too large and they would have to re-tool!
In 1990 I was privileged to be given a tour of this beast. 'Cool' but somewhat agricultural, I remember it most for the milk-bottle crates full of Vodka bottles to see the crew through a week in Farnborough!