Visits/Museum

Follow the journey taken by an Enigma message, from the moment of its interception to the point where the resulting intelligence was put to use in the field.

Bletchley Park Tour

Without intercepted information from the enemy, there can be no intelligence.

Encrypted Enigma messages were transmitted in Morse code - the combination of 'dots' and 'dashes' developed originally for the electric telegraph in 1843. These Morse messages were intercepted by the Y stations, the web of listening stations dotted around the country - and indeed the world - that provided Bletchley's codebreakers with their 'raw material' throughout the war. Wherever the Germans were, the Y stations were listening.

It was painstaking work, chasing up and down the frequencies in search of traffic. Accuracy of interception was vital. In particular, the preamble and the first three blocks were critical because they held the key to decoding the message. But many of the intercepted signals were weak, and several pairs of letters, such as U and V, are easily confused when transmitted in Morse.

Various methods were used by the German operators to evade interception, such as changes to the call sign, schedule time and opening frequency, and use of encoded frequency changes during transmission. These and other difficulties such as atmospheric conditions, keying style, and operating environment, all required the highest operating skills from the Y service intercept operator. Experienced operators grew to recognise the individual technique and idiosyncrasies of the German signallers - a person's style of transmitting Morse code is as individual as their voice. It is estimated that the Y service numbered some 8000 personnel, many of them civilians but also members of the WRNS, WAAF and ATS.

The intercepts were sent to Bletchley Park to be decoded and fitted together like a gigantic jigsaw puzzle.