Sarah Baring

“At the beginning of June 1944 electronics came to Bletchley. I was totally out of my depth there, but with various discreet questions from my esoteric sources, I gathered that our present Bombes were electromagnetic and that Professor Alan Turing, along with the electronic wizard T. E. Flowers of the Post Office Research Station at Dollis Hill, were working together desperately anxious to speed up the process of decipherment. Tommy Flowers decided to employ 1,500 thermionic valves instead of the electromagnetic relays. These apparently propelled the undertaking into the world of electronics and thus Colossus was born. The speed of decryption of this machine was remarkable and Colossus began operating at B.P. in February 1944, followed by Mark II using 2,400 valves. By the end of the war ten Colossi were in service at Bletchley. I am still bemused and confounded but thank God for Tommy Flowers and Alan Turing.”
― Sarah Baring, The Road to Station X: From Debutante Ball to Fighter-Plane Factory to Bletchley Park, a Memoir of One Woman's Journey Through World War Two