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


Tunny in action - 2

Source:  Robert Dowell, TNMOC

Tunny in action - 2

The cipher text would then be entered on the keyboard of the associated teleprinter and the plain text of the message would be output on the teleprinter paper. The German text was then translated by experts in German military language and sent on to London for use by the intelligence services. Much of the this codebreaking process was only declassified a few years ago and the full story from intercept to decryption has yet to be made public.


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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