Watch D-Day 80: The Allies Prepare from 10.15am on 5 June, hosted by Dame Helen Mirren in Portsmouth.
Secret code breakers
Bletchley Park, Bucks
Now the subject of numerous films and documentaries and visited by tens of thousands of people a year, this rambling late Victorian country pile and the huts and buildings in the surrounding grounds once housed an organisation so cloaked in secrecy that it would be decades before most people knew anything about it.
Bletchley Park was home to the Government Code and Cypher School – the secret organisation that decrypted coded enemy radio messages, firstly by hand and later with the help of the world’s first computers. By 1944, around 7,000 people were working here, three-quarters of them women, and they were handling an astonishing 5,000 intercepted messages a day.
The information supplied by Bletchley had already been crucial in helping the Allies counter the U-Boat threat during the Battle of the Atlantic; it would now prove to be of immense value during Operation Overlord. The signals decrypted here helped confirm the success of the plan to mislead the Nazis over where the landings would take place, enabled the Allies to build up a picture of the forces opposed to them, and gave their generals advance information about what the German commanders were planning. General Eisenhower would later write that
