Alastair Denniston
Scottish codebreaker who ran GC&CS from its founding in 1919 and moved it to Bletchley Park.
Denniston (1881–1961) was part of Room 40, the Admiralty's First World War codebreaking section, and in 1919 became head of its successor, GC&CS. Before the next war he recruited mathematicians and chess players rather than just linguists, and in July 1939 he was in Warsaw when the Poles handed over their Enigma work. He had also played field hockey for Scotland at the 1908 Olympics.
The organisation grew from a couple of hundred people to several thousand, and in 1942 Edward Travis replaced him as operational head. The usual verdict is that he was the right man to build the institution, but not to run a factory.