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Decoding the Enigma in Letchworth

PUBLISHED: 17:56 15 February 2010 | UPDATED: 14:57 20 February 2013

John Harper, far right, stands next to The Duke of Kent, second from the right. Far left is Professor Nigel Shadbolt, this year's President of the British Computer Society with some members of the rebuild team and women who worked as World War II WRNS Bom

John Harper, far right, stands next to The Duke of Kent, second from the right. Far left is Professor Nigel Shadbolt, this year's President of the British Computer Society with some members of the rebuild team and women who worked as World War II WRNS Bom

The Bombe played a vital role in World War II by decoding the messages sent by the German Enigma machine. Sue Fisher looks at how the masterpiece has been rebuilt to take its place in history

TWELVE years ago newly-retired engineer John Harper decided the quiet life was not for him. Instead he embarked on one of the most demanding tasks of his career, managing a project to rebuild a vital wartime machine.
The Bombe, also known as Cantab, or, for total secrecy, 6/6502, made it possible to decode the messages sent by the German Enigma machine which were intercepted at Bletchley Park. Knowing the enemy plans probably shortened the war by more than two years and the project was the subject of a recent Hollywood film starring Kate Winslet.
Although the story is well known now, it was kept totally secret for many years after the war and even people who worked on it didn't know what they were doing. That was certainly true of most of the 200-plus team based at ICL in Letchworth, who put together the Bombe.
John, who lives in Ickleford, worked at the British Tabulating Company, (later ICT and then ICL) in Stevenage and was aware of rumours about the nearby Letchworth factory. 'People kept hinting there was something special that Letchworth had done for the war effort,' he says. In time the full story began to emerge.
The Bombe was the brainchild of the brilliant Alan Turing, a key member of the hand-picked team of mathematicians, scientists and philosophers at Bletchley Park. They needed someone to perfect and build the machine, which would decode the messages being intercepted from the Germans. Looking for the right man, they came up with Harold 'Doc' Keen, chief engineer for the British Tabulating Company and the holder of more than 60 patents for his inventions.
The Doc, who earned his nickname because of the medical-style bag he carried, had joined the British Tabulating Machine Company in 1912 when he was just 18 and moved with them to Letchworth in 1921. The Bombe was to prove the most important project of his illustrious career involving what was described as a vast amount of thought and fantastically long hours. The machine was large and heavy, weighing a tonne and measuring a metre wide, a metre and a half high and two metres across. One adaptation, known as the giant, was constructed by putting four Bombes together and was too cumbersome to move from Letchworth.
Wiring for the Bombes was made by women working at the Spirella building while the frames were produced at the Government training centre in Pixmore Avenue. The final assembly was done at the company's main factory in Icknield Way, which has now been demolished to make way for Tabbs Close.
In all, 210 Bombes were built and taken to locations around the country in the utmost secrecy by a single soldier driving a lorry covered by a tarpaulin. This low-key approach was considered more secure than drawing attention to the cargo with armed escorts.
Doc Keen was given an OBE after the war and his principal assistant, H J Morton, was honoured with an MBE but no-one was told why. A certificate issued to thank key people stated, 'It will be gratifying to you to know that His Majesty's Lords Commissioners of the Admiralty have expressed their appreciation of the rapid and efficient production of the Cantab equipment which has materially assisted in the successful prosecution of the war.' It was signed by company chairman Raleigh Phillpotts who was given a knighthood.
Each and every Bombe was destroyed after the war and for 40 years the story remained a forgotten secret. But gradually the role that Bletchley Park, Letchworth and the Bombe had played in the war became public, Bletchley was opened as a museum and a group of enthusiasts decided to build a new Bombe.
John Harper became involved through his membership of the British Computer Society. 'I took early retirement and I wanted something special to do. This just intrigued me,' he says. It proved to be a major undertaking, keeping up to 60 people occupied for 12 years as well as requiring 65,000 in cash. The project actually cost up to 500,000 but many companies did work for nothing or at special rates.
'We started with people who lived round here coming to my living room,' says John.
They faced an enormous hurdle before they even started - they had the original component drawings that had been given to GCHQ after the war in 1946 but the assembly part drawings had been destroyed. It took two years to recreate them.
Countless hours of work followed over the next 10 years and included detailed research looking at academic papers here and in America as well as innovative engineering.
'It was interesting managing volunteers,' says John. 'Some were even more qualified than me, experts in their own field.' The replica Bombe, which includes thousands of components, was made in varied locations and then assembled at Bletchley Park earlier this year. It was officially unveiled by the Duke of Kent in July and will be on view to visitors in future. At last the vital role that Letchworth and its citizens played in winning the war is fully in the public domain.

Article taken from December issue of Hertfordshire Life

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