The computers that won the war: Bletchley Park's codebreaking equipment is rebuilt


The Heath Robinson

Source:  Robert Dowell, TNMOC

The Heath Robinson

The input stage comprised two sets of pulley wheels driving two loops of teleprinter tape in synchronism. One was the message tape and the other was a locally produced sequence of test patterns. The hole/no hole patterns on the tapes were read photo-electrically at up to 2000 characters per second and converted into electrical pulses. The pulse streams were compared by the electronics and a high speed counter generated the required output. (The machine on display at TNMOC is in the process of being rebuilt.) The Heath Robinson saved many days of tedious manual analysis but proved to be unreliable. All of the machines were designed and produced by the Post Office Research Station at Dollis Hill in north west London where, under the direction of Tommy Flowers, a much faster machine, Colossus, was designed. The aptly named Colossus was the world’s first electronic programmable computer. It was an incredible achievement and revolutionised the process of message decryption.


The Tunny Gallery, opened at The National Museum of Computing at Bletchley Park on 26 May 2011, tells the incredible story of the interception and decryption of German High Command radio teleprinter messages during World War Two. The gallery shows the entire wartime code-breaking process from intercept to decrypt and recognises the remarkable achievements of the men and women who contributed to the process in the 1940s. The centrepiece of the gallery is a fully functioning rebuild of a Tunny machine that produced the final decrypts of enciphered communications of the German High Command. The original Tunny, a British re-engineering of the then-unseen German Lorenz S42 cipher machine, was completed in 1942.

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