Bletchley Park

Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing. During World War II, Bletchley Park was the site of the United Kingdom’s main decryption establishment, the Government Code and Cypher School (GC&CS), where ciphers and codes of several Axis countries were decrypted, most importantly the ciphers generated by the German Enigma and Lorenz machines. It also housed Station X, a secret radio intercept station.

The high-level intelligence produced at Bletchley Park, codenamed Ultra, provided crucial assistance to the Allied war effort. Sir Harry Hinsley, a Bletchley veteran and the official historian of British Intelligence in World War II, said that Ultra shortened the war by two to four years and that the outcome of the war would have been uncertain without it.

A large portion of the site is now controlled by the Bletchley Park Trust. The National Museum of Computing, an independent voluntary organisation, rents space from the Trust to house its collection of historic computers. The museum is run by the Codes and Ciphers Heritage Trust (an independent registered charity) and is open to the public. It receives no Government or regional funding, or any of the Trust’s visitor or facility rental fees. The Bletchley Park Science and Innovation Centre (BPSIC) refurbished some of the historic structures and occupies part of the former code-breaker buildings. The site also houses the National Codes Centre. The main manor house is available for functions and is licensed for ceremonies. Part of the fees for hiring the facilities go to the Trust to maintain the site. Since 1967, Bletchley has been part of Milton Keynes.

Early history

The cottages in the stableyard were converted from a tack and feed house. Early work on Enigma was performed here by Dilly Knox, John Jeffreys and Alan Turing. The windows at the top of the tower open into a room used by Turing.

The lands of the Bletchley Park estate were formerly part of the Manor of Eaton, included in the Domesday Book in 1086. Browne Willis built a mansion in 1711, but this was pulled down by Thomas Harrison, who had acquired the property in 1793. The estate was first known as Bletchley Park during the ownership of Samuel Lipscomb Seckham, who purchased it in 1877. The estate was sold on 4 June 1883 to SirHerbert Samuel Leon (1850–1926), a financier and Liberal MP. Leon expanded the existing farmhouse into the present mansion.

The architectural style is a mixture of Victorian Gothic, Tudor and Dutch Baroque and was the subject of much bemused comment from those who worked there, or visited, during World War II. Leon’s estate covered 581 acres (235 ha), of which Bletchley Park occupied about 55 acres (22 ha). Leon’s wife, Fanny, died in 1937.

In 1938 the site was sold to a builder, who planned to demolish the mansion and build a housing estate. Before the demolition could take place, Admiral Sir Hugh Sinclair (Director of Naval Intelligence and head of MI6) bought the site. To cover their real purpose, the first government visitors to Bletchley Park described themselves as “Captain Ridley’s shooting party”.

The estate was conveniently located within easy walking distance of Bletchley railway station, where the “Varsity Line” between the cities ofOxford and Cambridge – whose universities supplied many of the code-breakers – met the (then-LMSR) main West Coast railway linebetween London and Birmingham, Manchester, Glasgow. Starting in 1938, Post Office Telephones laid dedicated cables, for numerous telephone and telegraph circuits, from the nearby repeater station at Fenny Stratford (on Watling Street, the main road linking London to the north-west, later to be designated the A5).


Original listening equipment in the 'Station X' room

The first wave of the Government Code and Cypher School (GC&CS) moved to Bletchley Park on 15 August 1939. The main body of GC&CS, including its Naval, Military and Air Sections, was on the ground floor of the mansion, together with a telephone exchange, a teleprinter room, a kitchen and a dining room. The top floor was allocated to MI6. The prefabricated wooden huts were still being erected, and initially the entire “shooting party” was crowded into the mansion, its stables and cottages. These were too small, so Elmers School, a neighbouring boys’ boarding school, was acquired for the Commercial and Diplomatic Sections.

Both of the two German electro-mechanical rotor machines whose signals were decrypted at Bletchley Park, Enigma and the Lorenz Cipher, were virtually unbreakable if properly used. It was poor operational procedures and sloppy operator behaviour that allowed the GC&CS cryptanalysts to find ways to read them.

The intelligence produced from decrypts at Bletchley was code-named “Ultra”. It contributed greatly to Allied success in defeating the U-boats in the Battle of the Atlantic, and to the British naval victories in the Battle of Cape Matapan and the Battle of North Cape. In 1941, Ultra exerted a powerful effect on the North African desert campaign, against the German army, under General Erwin Rommel. General Sir Claude Auchinleck stated that, but for Ultra – “Rommel would have certainly got through to Cairo”. Prior to the Normandy landings on D-Day in June 1944, the Allies knew the locations of all but two of the 58 German divisions on the Western front. Churchill referred to the Bletchley staff as “The geese that laid the golden eggs and never cackled”.

When the United States joined the war, Churchill and Roosevelt agreed to pool resources. A number of American cryptographers were posted to Bletchley Park and were inducted and then integrated into the Ultra structure, being stationed in Hut 3. From May 1943 onwards there was very close cooperation between the British and American military intelligence organisations.[9] Conversely, the existence of Bletchley Park, and of the decrypting achievements there, was never officially shared with the Soviet Union, whose war effort would have greatly benefited from regular decrypting of German messages relating to the Eastern Front. This reflected Churchill’s concern with security, and his distrust of and hostility to communism, even during the alliance imposed on him by the Nazi threat.

The only direct enemy action that the site experienced was when three bombs, thought to have been intended for Bletchley railway station, were dropped on 20–21 November 1940. One exploded next to the despatch riders’ entrance, shifting the rear end of Hut 4 (the Naval Intelligence hut) two feet on its base. As the huts stood on brick pillars, workmen just winched it back into position while work continued inside.

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