sg: “but I know what I’d rather have up front, RR, London, Derby, the known universe”. Most Merlins did not come from “proper” RR. Crewe was largely Paddies and colleens unfamiliar, on arrival, with any factory; as for Glasgow, well..:Hornby,Official History, Civil, Factories & Plant,P.290: Hives seen by Ministers as “courageous” agreeing to enter Red Clydeside with “some qualms whether (a name) synonymous with luxury (might arouse) antagonism”. Intended, like Crewe, for Vultures (!), it peaked at 5% fully Aero-skilled men. Both sites had Derby-detached supervisors…but they knew little of the specific product, and less about volume.

Ford/Trafford Park came to Hooker with “a problem”, involving, he assumed, tolerances beyond auto competence. Not so: inter-changeability of parts, essence of Model T et seq but alien in short-run Aero, required more precision than Royce had designed in. As dhfan says, it took them a year to redraw, then to churn out “very good” (Hooker) Merlins, cheaper than the parent by 30% Ritchie, Industry and Air Power,P.246 (in part due to scale): >”40 different Marks of Merlin were produced at Derby during the war. Ford produced just 5 (very similar) variants (yet) produced only 2000 fewer engines in 5 years than Derby produced in 7.”

cd: “…the quality of Bristol engines”. Same point: many Hercules came from Accrington – “diluted” hands plus exiled cider-quaffers. Many Hercules came from auto firms, co-ordinated by Austin: Ritchie,P.246: Ministry of Labour: “an object lesson (the) best monument of what can be done by careful Govt. planning and methodical industrial execution. Each site represents the highest attainment of the engineer’s art in mass production.” Hoover props, Bus garage Halifax, Spit: miraculous that our grandmothers delivered what they did.