2012 - Bletchley Park

(Photo: Nick Withers)

June 2012: Bletchley Park

Some 50 members of the Oxted & District History Society and their friends enjoyed their summer outing to Bletchley Park, Buckinghamshire, the home of wartime signals intelligence. Those attending had to dodge the showers but left at the end of the day with a fascinating insight into wartime intelligence operations. They visited the newly built replicas of the ‘Bombe’ and ‘Colossus’.

Bletchley Park was the former country home of Sir Herbert Leon, a wealthy London financier and Liberal MP. With its extensive grounds and position near good rail and road communications, it was ideally placed to become an intelligence centre. By 1938 the house and estate were in the hands of developers and Government intervention was necessary to secure the site for the intelligence services.

The first arrivals from the Government Code and Cypher School came in August 1938 with a mission to crack the Nazi codes. A German had offered to sell the secrets of the Enigma coding machine in 1931 but the British and French did not take up the offer. However the Poles did, cracked the Enigma code and passed this intelligence to the British in July 1939, just before the outbreak of World War II. There is a memorial to the Polish code-cracking pioneers at Bletchley Park. However the Enigma code was only altered every few months before the war, but, with the advent of war, the codes changed daily.

An intelligence team, working undr Dilly Knox, which included John Jeffreys and Alan Turing, cracked the ‘green’ German Enigma code in January 1940 and then the ‘red’ code used by the Luftwaffe. In April 1940 the Germans invaded Denmark and Norway and Bletchley Park broke the ‘yellow’ German Army cipher.The breaking of Enigma was aided by a complex electro-mechanical device called the ‘Bombe’ , devised by Turing, based on the earlier Polish ‘Bomba’. The Bombe ran through every possible code permutation to determine the German daily Enigma settings. Turing was joined by Hugh Alexander, a British chess grandmaster, to decipher the German Navy Enigma code.

At first the British commanders were reluctant to take the intelligence seriously but throughout the First Battle of the Atlantic the information helped the Admiralty to track the U-boat packs, considerably reducing their ability to sink merchant navy ships bringing vital supplies to Britain from America. A unit at Bletchley Park also broke the Japanese ciphers, enabling the code-breakers to monitor Japanese preparations for war.

The German attack on the Soviet Union in June 1941 brought some of the most distressing messages Bletchley Park ever managed to break, the massacre of tens of thousands of Jews. The evidence was collected for use in the war crimes trials after the war. In 1942 the code-breakers successes enabled the Royal Navy to cut Rommel’s supply lines in North Africa and keep Montgomery informed about Rommel’s every move.

In early 1942 the U-boats introduced a more complex Enigma cipher but this had been broken by the end of 1942. The construction by Tommy Flowers and his team of Post Office engineers of Colossus, the world’s first programmable electronic computer in December 1943, enabled Bletchley Park to glean details of German defences for the D-Day invasion and allowed the British to dupe Hitler over where the Allies were to land. Early in June 1944 he withdrew some troops from Normandy to Calais, where he expected the Allies to land.

By the end of World War II there were 10,000 people working at Bletchley Park. They did not win the war but certainly shortened it, saving countless lives and left us with the computer technology which dominates our lives today.