D-Day: Interception, Intelligence, Invasion - a new 75th anniversary exhibition at Bletchley Park

Fifteen years ago I was part of a BBC team covering the 60^th anniversary of the Normandy landings. We crossed the Channel in the Royal British Legion’s chartered vessel, the MV Van Gogh, along with some 450 veterans and their families (above). Halfway across we watched as a Lancaster bomber flying overhead dropped a million poppies in memory of those who lost their lives in that operation and stood in silence to remember them. Later, the Queen, who attended the Normandy ceremonies along with 16 other heads of state, described the 1944 invasion of France as “one of the most dramatic military operations in history”.

What many of us didn’t know at the time was that its ultimate success owed much to a group of code-breakers many miles away in Bletchley Park in Buckinghamshire (above). For 18 months they had worked in shifts around the clock, decrypting enemy messages that helped build up an exact picture of the defences the Allied forces were likely to meet, including the likely level of resistance, the location of landmines, and even the height of fences. They had also fed out false information which convinced Hitler any invasion would be further down the coast at Calais, and as a result, he had stationed the bulk of his troops there. D-Day: Interception, Intelligence, Invasion tells their story.

The unit had been set up in 1939, when the Government bought Bletchley Park to house the 150 or so staff of the secret codebreaking and intelligence efforts of the Government Code and Cypher School (GC&CS). As more staff were recruited, huts were built in the grounds. Eventually more than 9000 people worked there.

The first major success came in 1941 when they managed to break the codes used by the German Enigma machine (above). This later featured in the 2014 film, The Imitation Game, with Benedict Cumberbatch as computer scientist Alan Turing. But official secrecy meant the public knew little about their later achievements.

D-Day exhibition © Andy Stagg

This exhibition, housed in the complex's restored Teleprinter building, restores the balance and gives a picture of the build-up to D-Day with original decoded messages such as the German naval one (below) that alerted Hitler to what was happening. “Immediate readiness”, it says. “There are indications that the invasion has begun.”

Intercepted message ©Bletchley Park Trust

A 12-minute immersive film, shown on a 22m-long screen, tells the many stories of Operation Overlord, including how the 15,000 men of the 82nd US Airborne Division had their drop zone moved just a few weeks before D-Day to avoid a German division, thanks to Bletchley intelligence.

D-Day film ©Andy Stagg

The code-breakers' work was relentless. Intercepted communications came from secret listening posts all over the country, and each one, whether a request for aviation fuel or details of a troop train, was logged, indexed and cross-referenced. Sometimes the most innocuous message contained a vital clue. An application for leave from a German soldier in a unit in Russia was rejected by Field Marshal Gerd von Rundstedt, who was in Paris. From this the team in Hut 3, the main reporting centre for messages, deduced that the unit was now under his command and was being moved to his territory in the west. Hitler never knew about Bletchley Park or that his top-secret codes were being broken. Cover stories to disguise the origins of information were used, such as 'a reliable source recovered a flimsy bit of a message in the wastepaper basket of....'. On occasion reconnaissance aircraft were sent out, just so they could be spotted by the enemy.

Mavis Batey © The Batey family

The exhibition also honours some of the key code-breakers, among them Mavis Batey, above. (Three-quarters of the staff were women.) Her team reconstructed the wiring and encryption settings of an Abwehr German Intelligence machine, making it possible to tell to what extent the enemy believed Allied deception messages, both before and after D-Day.

The exhibition forms part of the wider Bletchley Park experience. Exploring the grounds, you can visit the Library (above), once home of the Naval section, see wartime vehicles in the garages, tour restored huts where the code-breakers were based, and learn about their experiences through an oral history project. Cipher machines, including Enigma, are on display in the museum. Winston Churchill visited Bletchley in 1941 and dubbed the code-breakers “the geese that laid the golden eggs .... but never cackled”. It’s only now, 75 years after D-Day, that thanks to recently declassified documents and to remaining codebreakers ending decades of silence, the full story behind the landing is emerging.


Admission to D-Day: Interception, Intelligence, Invasion is included in Bletchley Park admission tickets: £20, valid for a year. (Concessions available; children under 12 free.)
An excellent book by Bletchley Park’s research historian, Dr David Kenyon, D-Day: Interception, Intelligence, Invasion accompanies the exhibition.
https://bletchleypark.org.uk