Open main menu

William Gordon Welchman (15 June 1906 – 8 October 1985) was an English mathematician, university professor, Second World War codebreaker at Bletchley Park and author. After the war he moved to the US, and later took American citizenship.[1]

Gordon Welchman
Gordon Welchman.jpg
Born(1906-06-15)15 June 1906
Fishponds, Bristol, England
Died8 October 1985(1985-10-08) (aged 79)
OccupationMathematician, codebreaker, author


Early life, education and careerEdit

Gordon Welchman was born, the youngest of three children, at Fishponds in Bristol, to William Welchman (1866–1954) and Elizabeth Marshall Griffith. William was a Church of England priest who had been a missionary overseas before returning to England as a country vicar, eventually becoming archdeacon of Bristol. Elizabeth was the daughter of another priest, the Revd Edward Moule Griffith.[2]

Welchman was educated at Marlborough College and then studied mathematics as a scholar at Trinity College, Cambridge, from 1925 to 1928.[3] In 1929, he became a Research Fellow in Mathematics at Sidney Sussex College, Cambridge, a Fellow in 1932 and later Dean of the College.

Bletchley ParkEdit

Just before the Second World War, Welchman was invited by Commander Alastair Denniston to join the Government Code and Cypher School at Bletchley Park, in the event of war. He was one of four early recruits (the others being Alan Turing, Hugh Alexander and Stuart Milner-Barry), who all made significant contributions at Bletchley and who became known as "the wicked uncles". They were also the four signatories to an influential letter, delivered to Winston Churchill in October 1941, asking for more resources for the code-breaking work at Bletchley Park. Churchill responded with one of his "Action This Day" written comments.

As stated in his book, most of his work at Bletchley was centred on what was known as "traffic analysis" of encrypted German communications. This is roughly described as the practice of examining parts of messages that are standardised descriptors or headers, such as message origination, message destination, time/date information, and so on, especially as messages always require such information. Most cryptographers agree this is markedly easier than attacking cryptographic ciphers directly (although still very complicated and mathematically intensive processing is needed to make initial discoveries), and Welchman is credited with innovating the approach. This led to data analysis techniques that today we describe as metadata analysis.

Welchman envisaged an enhancement to Alan Turing's improved design of the Polish electromechanical Enigma cipher-breaking machine, the bombe. Welchman's enhancement, the "diagonal board", which exploited the self-reciprocity of the Enigma machine, made the device substantially more efficient; this was an implementation of the simple fact that if B is Steckered (plugged) to G then G is also Steckered to B. If 26 rows of 26 way connectors are stacked up, then any connection point can be referenced by its row letter and column letter. A physical piece of wire can now connect row B element G to row G element B. The device was called a Diagonal Board because such a piece of wire is diagonally across the matrix of connections. The Diagonal Board cut decipher times down from days to mere hours when attacking ciphers generated by the German Enigma machine. Bombes became the primary mechanical aid in breaking Enigma ciphers during the war, by speeding up the search for current wheel order settings being used with the Enigma machines. Wheel order settings were changed often, initially at least once per day.

Welchman was head of Hut Six, the section at Bletchley Park responsible for breaking German Army and Air Force Enigma ciphers.[4] During his time at Bletchley, Welchman opposed engineer Tommy Flowers' efforts on the Colossus computer (the world's first programmable electronic computer) because Colossus used vacuum tubes.[5]

In 1943, he became assistant director in charge of mechanisation and also had responsibility for cryptographic liaison with the US.


Soon after the end of the war Welchman took up Hugh Alexander's old post as director of research for the John Lewis Partnership[6] before then moving to the United States in 1948 where he taught the first computer course at MIT in the United States. He followed this by employment with Remington Rand and Ferranti.[4] Welchman became a naturalised US citizen in 1962. In that year, he joined the Mitre Corporation, working on secure communications systems for the US military. He retired in 1971, but was retained as a consultant.

In 1982 his book The Hut Six Story[4] was published, initially by McGraw-Hill in the US and by Allen Lane in Britain. The National Security Agency disapproved. The book was not banned, but Welchman lost his security clearance (and therefore his consultancy with MITRE) and was forbidden to discuss either the book or his wartime work.[7]

Welchman died in 1985; his final conclusions and corrections to the story of wartime code breaking were published posthumously in 1986 in the paper "From Polish Bomba to British Bombe: the birth of Ultra" in Intelligence & National Security, Vol 1, No l. The paper was included in the revised edition of The Hut Six Story published in 1997 by M & M Baldwin.[4]

Personal lifeEdit

In 1937 Welchman married Katharine Hodgson, a professional musician, the daughter of Francis Faith Hodgson, who was a captain in the Indian Army. The couple had a son and two daughters.

In 1959 Welchman divorced Katharine and married the American Cubist painter Fannie Hillsmith. The marriage lasted until 1970.[8] Fannie was the daughter of Clarence Hillsmith, a consulting engineer from New Hampshire.

In 1972 he married Elisabeth Huber, daughter of Anton Wilhelm Huber, a sawmill owner and carpentry contractor from Bavaria, and his wife, Myrtle Octavia Hussey, who was Welchman's second cousin.[2]


Gordon Welchman was the subject of a BBC documentary broadcast on BBC Two on 7 September 2015.[9] The programme was entitled Bletchley Park: Code-breaking's Forgotten Genius[10] and as The Codebreaker Who Hacked Hitler when broadcast on the Smithsonian Channel.[11] The documentary notes that traffic analysis is now known as "network analysis" and "metadata" analysis and gives as an example the location of Osama bin Laden by the use of network analysis.

The withdrawal of his security clearance in 1982, by the NSA, after the publishing of his 'Hut 6' book, was described as "devastating".[9] On 26 September 2016, a blue plaque was unveiled by his daughter, Susanna Griffiths, at St Mary's Church, Fishponds, in Bristol. Speaking at the event, the Director of GCHQ Robert Hannigan acknowledged the harsh treatment of Welchman and paid tribute to his "immense contribution" as a "giant of his era".[12]

See alsoEdit


  1. ^ Greenberg, Joel (2014). Gordon Welchman: Bletchley Park's Architect of Ultra Intelligence. Frontline Books. ISBN 978-1848327528.
  2. ^ a b University of St Andrews – Welchman
  3. ^ Denniston, Robin (2004). "Welchman, (William) Gordon (1906–1985)". Oxford Dictionary of National Biography. Oxford University Press.
  4. ^ a b c d Welchman, Gordon (1984) [1982]. The Hut Six story: Breaking the Enigma codes. Harmondsworth, England: Penguin Books. ISBN 0-14-00-5305-0. An early publication containing several misapprehensions that are corrected in an addendum in the 1997 edition.
  5. ^ McKay, Sinclair The Secret Life of Bletchley Park (2010, Aurum Press, London) pp 266–8 ISBN 9781845135393
  6. ^ "Bletchley Park Roll of Honour – Gordon Welchman". Bletchley Park. Retrieved 24 January 2016.
  7. ^ West, pg. 26-28, and 310-319
  8. ^ Smith, Roberta (4 August 2007). "Fannie Hillsmith, Distinctly American Cubist, Dies at 96". The New York Times. Retrieved 2 September 2015.
  9. ^ a b BBC documentary
  10. ^ Narrator: Steven Mackintosh, Contributors: John Naughton, Cynthia Storer, Producer and Director: Russell England (7 September 2015). "Bletchley Park: Code-breaking's Forgotten Genius". Make It Digital Season. BBC Two.
  11. ^ "The Codebreaker Who Hacked Hitler" Smithsonian Channel website
  12. ^ "Gordon Welchman, no longer a forgotten hero". Downend Voice. 28 October 2016. Retrieved 9 May 2017.


  • Russell-Jones, Mair (2014), My Secret Life in Hut Six: One Woman's Experiences at Bletchley Park, Lion Hudson, ISBN 978-0-745-95664-0
  • Welchman, Gordon. The Hut Six Story: Breaking the Enigma Codes. 2nd Revised edition (December 1997). M.& M.Baldwin. ISBN 978-0947712341.
  • West, Nigel (1986). The Sigint Secrets: The Signals Intelligence War, 1900 to Today--Including the Persecution of Gordon Welchman. New York: William Morrow and Company. ISBN 0-688-07652-1. LCCN 88-43153.