William Francis "Nobby" Clarke (1883–1961) was a British intelligence officer and cryptographer of naval codes in both World Wars.
Clarke was educated at Harrow School and Magdalen College, Oxford, and trained as a lawyer, being admitted to the bar in 1906 by his father, Sir Edward Clarke, a prominent lawyer and later Solicitor-General.[1]
In 1915, he was commissioned as an assistant paymaster, having failed the eye examination for executive officer. He knew German, and in March 1916 joined Room 40.[1] His talent was for information analysis rather than code-breaking. He was on duty during the Battle of Jutland, and was unimpressed by the inefficient handling and distribution of intelligence. When Clarke and Francis Birch were chosen in 1919 to write a history of Room 40, their outspoken criticism of the Navy's mishandling of intelligence led to the history being allegedly "suppressed".[1]
In 1919, Clarke joined the Government Code and Cipher School, working for four years on American diplomatic traffic. In 1924 he was promoted to head of the new naval section in GC&CS, holding the position to 1941. He was succeeded as head by his colleague Francis Birch, and then concentrated on Italian naval codes, retiring in October 1945.[1]
Clarke died in 1961, and he was buried at Church of All Saints, Selworthy.[1]