Evidence of prior mass-production of the Rolls-Royce Merlin:- "... the preponderance of unskilled labour at Glasgow rendered the factory particularly reliant on up-to-date production methods and mechanisation. Machine tools were arranged and set for single-purpose operations, and the factory was planned on a flow production basis, with the minimum of rehandling." (Ritchie, Sebastian Industry and Air Power. The Expansion of British Aircraft Production, 1935-1941, Frank Cass, 1997, p135) Rolls-Royce Glasgow was operational by February 1941. (ibid, p135 & p144)