Royal Mail commemorates Colossus – a giant achievement in code-breaking

(19 February 2015)Royal Mail has issued a stamp to commemorate Colossus – the world’s first electronic, digital and programmable computer. This is part of the Inventive Britain set of Special Stamps, issued on 19 February 2015. The stamps are on sale now from Royal Mail by phone on 03457 641 641 or from and available from 8,000 Post Offices nationwide.

The Colossus stamp has a close association with Royal Mail, as it was designed and built by engineer Tommy Flowers MBE and his team at the General Post Office (GPO), a precursor to Royal Mail.

Born in east London in December 1905, Flowers joined the telecommunications branch of the GPO in 1926, moving to work at the GPO Research Station at Dollis Hill in north-west London in 1930.

Flowers’ first contact with the wartime codebreaking effort came in February 1941 when his help was requested by Alan Turing, who was then working at the Government’s Bletchley Park codebreaking establishment in Buckinghamshire. Turing wanted Flowers to build a decoder for the relay-based Bombe machine, which Turing had developed to help decrypt the Germans’ Enigma codes.

Although the decoder project was abandoned, Turing was impressed with Flowers’ work, and in February 1943 introduced him to Max Newman who was leading the effort to automate part of the decoding of the Lorenz cipher. This was a high-level German cipher generated by a teletypewriter in-line cipher machine, called “Tunny” by the British. It was a much more complex system than Enigma; the decoding procedure involved trying so many possibilities that it was impractical to do this by hand. Flowers and Frank Morrell (also at Dollis Hill) designed the first machine, to decrypt the Lorenz machine cyphers, which they christened “Heath Robinson”.

“Tunny” messages from Lorenz machines were first intercepted by the British in June 1941. After a year-long struggle, Bletchley Park had its first successes in deciphering the code in 1942.


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