William Francis 'Nobby' Clarke (1883 - 1961) was a British intelligence officer and cryptographer of naval codes in both World Wars.

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

Room 40

In the history of Cryptanalysis, Room 40 was the section in the Admiralty most identified with the British cryptoanalysis effort during the First World War.Room 40 was formed in October 1914, shortly after the start of the war...

. His talent was for information analysis rather than code-breaking. He was on duty during the Battle of Jutland

Battle of Jutland

The Battle of Jutland was a naval battle between the British Royal Navy's Grand Fleet and the Imperial German Navy's High Seas Fleet during the First World War. The battle was fought on 31 May and 1 June 1916 in the North Sea near Jutland, Denmark. It was the largest naval battle and the only...

, and was unimpressed by the inefficient handling and distribution of intelligence. When Clarke and Francis Birch

Francis Birch (cryptographer)

Francis Lyall Birch was a British cryptographer. He was educated at Eton and King’s College, Cambridge. He was awarded an OBE in 1919 and CMG in 1945....

 were chosen in 1919 to write the history of Room 40, their outspoken criticism of the Navy’s mishandling of intelligence led to the history being “supressed”.

In 1919 he 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

Francis Birch (cryptographer)

Francis Lyall Birch was a British cryptographer. He was educated at Eton and King’s College, Cambridge. He was awarded an OBE in 1919 and CMG in 1945....

, and then concentrated on Italian naval codes, retiring in October 1945.

He was educated at Harrow School

Harrow School

Harrow School, commonly known simply as "Harrow", is an English independent school for boys situated in the town of Harrow, in north-west London.. The school is of worldwide renown. There is some evidence that there has been a school on the site since 1243 but the Harrow School we know today was...

 and Magdalen College, Oxford

Magdalen College, Oxford

Magdalen College is one of the constituent colleges of the University of Oxford in England. As of 2006 the college had an estimated financial endowment of £153 million. Magdalen is currently top of the Norrington Table after over half of its 2010 finalists received first-class degrees, a record...

 and trained as a lawyer, being admitted to the bar in 1906 by his father Edward George Clarke

Edward George Clarke

Sir Edward George Clarke QC QC was a British barrister and politician, considered one of the leading advocates of the late Victorian era and serving as Solicitor-General in the Conservative government of 1886–1892...

a prominent lawyer and later Solicitor-General.