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Sirens Silk and Spitfires
Letchworth and the Second World War
Letchworth's Enigma
Many people are familiar with the name ENIGMA, the machine used by the Germans to send messages in Morse Code. The enigma machine could scramble a code in over 150,000,000,000 000,000,000 ways! It was vital that the allies crack this code in order to win the war. However, fewer people have heard of the Bombes and that these amazing machines were made in Letchworth.
The German Enigma signals were intercepted by the Government Code and Cypher School which was based at Bletchley Park, a Victorian Mansion in Buckinghamshire. Top mathematicians such as Gordon Welchmann and Alan Turing had been working with Polish intelligence who had built a decoding machine called a ‘Bomba'. They believed that they could improve upon the Polish design using electro-mechanics and so contacted the British Tabulating Machine Company of Letchworth to create a new machine which would be known as the Bombe. In BTM the project was known to the few people in the know as the CANTAB project.
Four prototype machines had been built at Letchworth by the Summer of 1940. The first Bombe was called Victory. A year later there were around 6 Bombes in operation at Bletchley Park in Hut 11. The Bombes were large, about 1 metre high, 2 metres long and 1 metre wide and weighed around one ton. They were delivered to their locations on ordinary lorries covered with tarpaulin so as not to arouse suspicion. One machine, designed to interpret the Naval Enigma, was made by linking four Bombes together. Known as the ‘Giant' it was too heavy to move and so was operated at the Letchworth factory. When it achieved a result, a special number to Bletchley Park was telephoned with the message ‘the giant has caught a whale'.
Production increased and so in Spring 1942 they took over the Ascot Training Centre and a month later took up further space at the Spirella Factory. At Spirella teams of several hundred staff, predominately women, worked day and night assembling unique wired rotors. By 1942 BTM were producing at least one Bombe per week.
Eventually the decoding operation required more space and so in 1943 operations were moved to Stanmore and Eastcote and the Bombes at Bletchley Park remained purely for training purposes. Around 1200 WRNS were housed at Stanmore and Eastcote to operate the machines.
Around 210 Bombes were built in total. Although Colossus had the glamour of being the first computer and decoding Hitler's secret high-command wireless, it was the Bombes that decoded the ‘unbreakable' Enigma machine and so heralded the success of many allied missions. All the Bombes were destroyed after the war and many people who lived in Letchworth at the time, including BTM employees, were probably unaware of the important and valuable work they were undertaking.
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| BTM staff working at the Spirella Factory creating intricate wiring systems |
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| Women working for BTM at the Spirella Factory |
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