Bletchley Park: Code-breaking's Forgotten Genius

Bletchley Park: Code-breaking's Forgotten Genius

The story of Gordon Welchman, and his part in both organisation, and improving the cypher breaking machinery, was told on BBBC 2 on Monday night. He has been the forgotten hero, airbrushed out of “The Imitation Game”, and his book suppressed.

He was a brilliant mathematician, easily Alan Turing’s equal, and while the mechanical cipher solving machines – the “bombes “ could take days, and the German codes changed at midnight, he introduced the “diagonal board”.

This change made the devices substantially more efficient in the attack on ciphers generated by the German Enigma machine, so that they could be solved in hours rather than days. The modified machine became knows as the Turing-Welchman Bombe.

Apart from his abilities in mathematics he became particularly known for his excellent organising skills. The Welchman proposal was for the following organization which remained basically unchanged throughout the War.

- Army/Air Force Code breaking Hut 6.
- Army/Air Force Intelligence Hut 3.
- Naval Code breaking Hut 8.
- Naval Intelligence Hut 4.

The Hut numbers became the cover for these activities. Welchman said later that this was probably his greatest contribution to the War effort.

Another important part of the work which he initiated was “Traffic analysis” where by all incoming intercepts received from the Y Stations were meticulously logged and cross indexed to build up a detailed picture of the signals from all parts of the German Forces.

Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication. It can be performed even when the messages are encrypted and cannot be decrypted. It is still in use by intelligence groups today.

His last assignment was to write an official – albeit secret – history of Hut 6, and develop plans for the successor to Bletchley Park, the intelligence gathering agency GCHQ.

Welchman had the misfortune to be living in the United States, and when he published his book “Hut 6”, in 1982, he faced the full wrath of the National Security Agency. Unlike Mrs Thatcher’s attempts to ban “Spy Catcher”, the American agency went for the jugular, threatening Welchman with imprisonment should he discuss with the media either the book or his wartime work. That meant any promotion was out of the question, and the book sank without trace, remaindered and pulped. He also lost his security clearance. So much for the "land of the free"; Welchman saw the darker side of the American State machinery.

This was a compelling story, about someone whom I had hitherto known nothing. It is always amazing the way history keeps throwing up the unexpected, and shining new light on areas where everything seemed to have been told.