Who's Who - Sir William Hall

Copy of the Zimmermann Telegram Sir William Reginald Hall (1870-1943), known as "Blinker", on account of a chronic facial twitch, served with British naval intelligence during World War One and was most notably successful in decrypting the Zimmermann Telegram of 1917.

Hall joined the Royal Navy in 1884, reaching the rank of Commander in 1898 and Captain in 1905.  From 1906-07 he was an inspector of mechanical training; and from 1911-13 he served as Assistant Controller to the Royal Navy.

The outbreak of the First World War brought Hall an appointment in October 1914 as Director of Naval Intelligence (as much as anything else for reasons of ongoing ill-health).  As such he founded (with Sir Alfred Ewing) the famous British naval intelligence office 'Room 40', quickly establishing radio-finding stations along Britain's east and south-east coasts.

Room 40 was responsible for a series of important naval decrypts at the Battle of Jutland in May/June 1916 (which were largely misused by the Admiralty) and, rather more spectacularly, in deciphering the Zimmermann Telegram in 1917 (which suggested a German plot to assist Mexico is annexing U.S. territory).  The latter helped to bring the U.S. into the war on the side against the Central Powers.  Room 40 also played a notable role in securing the capture of British traitor (and Irish patriot) Sir Roger Casement.

Perhaps as significantly, the German Navy's Magdeburg codebook, which detailed its operating ciphers and codes, had been captured early in the war and Hall's cryptographers used it against all intercepted transmissions of the German fleets.  Thus the Royal Navy knew the position of every German ship for almost the entire duration of the war.

Hall instigated a policy of ensuring co-operation with other British intelligence departments, exchanging data with MI5, MI6 and Scotland Yard's Special Branch.

Hall was knighted in 1918 in recognition of his efforts in the Zimmermann affair and promoted to Rear-Admiral.  Retiring from the Royal Navy the following year he entered Parliament the same year as Conservative M.P. for West Derby, Liverpool.

During the 1920s and 30s Hall travelled extensively to the U.S. to give lectures on intelligence gathering matters.  Too old to undertake active service when war broke out again in 1939 Hall nevertheless served in the British Home Guard, a post he held until his death in 1943.

A "dogfight" signified air combat at close quarters.

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