June 2021 

By late May 1940 the Germans have arrived at the French coast, cutting the Allied forces in two. Their risky invasion plan ‘Fall Gelb’ (or ‘Case Yellow’) has paid off.  For the Allies, things will only get worse - an evacuation of the British forces from Dunkirk, the capture of Paris and the ultimate humiliation at Compiègne.

It also marked a turning point for Bletchley Park. The attack led the Germans to change their Enigma procedures which had been exploited so successfully by the Hut 6 team. It took a creative approach, as well as some lazy enemy operating procedures, to restore Bletchley Park’s capability in reading German messages.

In the second part of this special ‘It Happened Here’ episode, Dr Thomas Cheetham guides us through the dramatic world events that could have seen Bletchley Park lose the ability to read Enigma for the rest of the war. 

Special thanks go to Gus Munro and Dr Ben Thomson for voicing our archival documents.

©Bletchley Park Trust 2021

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