William Gordon Welchman (15 June 1906 - 8 October 1985) was a British
mathematician, university professor and author. During World War II
he was a codebreaker at Bletchley Park (BP) where he became the head of
Hut Six. After the war, he moved to the United States and became a US citizen.
In 1982 he published the Book The Hut Six Story 
about his wartime work in the UK.
Gordon was born on 15 June 1906 in Bristol (UK),
son of Reverend William and Elizabeth Welchman. From 1920 to 1925
he went to Marlborough College on a scholarship, where he won a
mathematics scholarship to Trinity College in Cambridge (UK).
From 1925 to 1928 he studied at Trinity College and in 1929 he became a
Research Fellow in mathematics at Sidney Sussex College,
also in Cambridge, where he later became a Fellow (1932) and finally Dean.
Life and work at Blecthley Park was divided into Huts, small hastily
erected buildings that were spread all over the park. Each hut had a number.
Hut 6 was responsible for breaking the
of the German Army and Air Force.
Once they were broken, the messsages were sent to Hut 3 for translation and
The intelligence derived from the intercepts became known
as Top Secret Ultra or Ultra.
A level of secrecy that surpassed even Top Secret.
Churchill had commanded that the source of this intelligence should
be protected at all cost.
After his arrival at Bletchley Park in 1939, Welchman got
involved in breaking the German Army and Air Force codes
and would soon become responsible for setting up and organising Hut 6.
In 1940 he made a significant contribution to the
machine that was developed by fellow mathematician Alan Turing and that
was used for breaking the Enigma cipher.
By adding a so-called diagonal board, the time of a Bombe run was
greatly reduced, and the modified machine became knows as the
In October 1941, resources and budgets at Bletchley Park had become so tight,
that the four wicked uncles, Turing, Alexander, Milner-Barry and Welchman,
saw themselves forced to write a letter directly to the Prime Minister,
Winston Churchill. This went completely against the military hierarchy
at the time. In the letter they asked for more resources for the
important codebreaking work at BP. Churchill's response to the letter
was the now famous comment Action this Day.
Welchman remained at BP for entire war.
Apart from his abilities in mathematics he became particularly known for
his excellent organising skills. When the war was over, his last assignment
was to write down the official Hut 6 history and to develop plans for
the post-war successor to GC&CS: The
Government Communications Headquarters (GCHQ),
which still exists today.
Shortly after WWII, in 1948, Welchman moved to the United States
where he lectured computer technology at MIT. He later worked for
Remington Rand and Ferranti and became a US citizen in 1962.
Later that year he joined MITRE Corporation,
where he worked on secure communication for the US military.
Although he retired in 1971, he remained a consultant for many years.
After Frederick Winterbotham
had published his book The Ultra Secret in
1974 , in which the existence of
Bletchley Park was revealed,
Welchman thought the time was right to talk about his wartime work
as a codebreaker. In 1982 he published his book The Hut Six Story 
in which he gave a detailed account of the organisation of Hut 6 and
the technical backgrounds to the Bombe.
Although 37 years had passed since the end of WWII, the book caused upset
with the National Security Agency (NSA)
in the US. Although the book was not banned,
Welchman was forbidden to discuss it - and his wartime work -
in public. Furthermore, he lost his security clearance in the
United States and could therefore no longer work as a consultant for MITRE.
In 1985 he died in Newburyport (Massachusetts, USA) at the age of 79.
His conclusions and corrections to the story of wartime codebreaking
were published in a paper a year later. They are included in the revised
1997 edition of The Hut Six Story .
- Gordon Welchman, The Hut Six Story
1982. Revised edition M&M Baldwin 1997. ISBN 0-947712-34-8.
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