Editing Bletchley Park (section)

==History==
===Preparation for War===
[[File:bp-polish-codebreakers-plaque.jpg|thumb|Bletchley's Polish Memorial, commemorating "the [prewar] work of [[Marian Rejewski]], [[Jerzy Różycki]] and [[Henryk Zygalski]], mathematicians of the [[Biuro Szyfrów|Polish intelligence service]], in first breaking the Enigma code. Their work greatly assisted the Bletchley Park code breakers and contributed to the Allied victory in World War&nbsp;II."]]

A mansion was first built here in 1711, with the current house built in the 1870s.<ref>{{Cite web|url= https://www.heritagegateway.org.uk/Gateway/Results_Single.aspx?uid=1222785&resourceID=19191|title=Bletchley Park House|publisher=Heritage Gateway|website=www.heritagegateway.org.uk|access-date=14 December 2021}}</ref> In 1938, the mansion and much of the site was bought by a builder for a housing estate, but in May 1938 Admiral Sir [[Hugh Sinclair]], head of the [[Secret Intelligence Service]] (SIS or [[MI6]]), bought the mansion and {{convert|58|acre|ha}} of land for £6,000 (£{{Inflation|UK|6000|1938|r=-3|fmt=c}} today) for use by Code and Cypher School and SIS in the event of war. He used his own money as the Government said they did not have the budget to do so.<ref>{{Harvnb|Morrison|pp=102–103}}</ref>

A key advantage seen by Sinclair and his colleagues (inspecting the site under the cover of "Captain Ridley's shooting party")<ref>{{Harvnb|McKay|2010|p=11}}</ref> was Bletchley's geographical centrality. It was almost immediately adjacent to [[Bletchley railway station]], where the "[[Varsity Line]]" between [[Oxford]] and [[Cambridge]]{{snd}}whose universities were expected to supply many of the code-breakers{{snd}}met the main [[West Coast Main Line|West Coast railway line]] connecting London, [[Birmingham]], [[Manchester]], [[Liverpool]], [[Glasgow]] and [[Edinburgh]]. [[Watling Street]], the main road linking London to the north-west (subsequently the [[A5 road (Great Britain)|A5]]) was close by, and high-volume communication links were available at the telegraph and telephone repeater station in nearby [[Fenny Stratford]].<ref>{{cite web|url=http://discovery.nationalarchives.gov.uk/details/r/C2135171|title=Fenny Stratford Telephone Repeater Station. Erection. A. Cole Ltd.|publisher=National Archives|access-date=13 October 2018}}</ref>

Five weeks before the outbreak of war, Warsaw's [[Biuro Szyfrów|Cipher Bureau]] revealed [[Cryptanalysis of the Enigma|its achievements]] in breaking Enigma to astonished French and British personnel.<ref name="Milner-Barry1993P92"/> The British used the Poles' information and techniques, and the [[Polish Enigma doubles|Enigma clone]] sent to them in August 1939, which greatly increased their (previously very limited) success in decrypting Enigma messages.<ref>{{Harvnb|Twinn|1993|p=127}}</ref>

=== Early work ===
[[File:Information Flow Bletchley Park Enigma Messages.png|thumbnail|right|upright=1.5| Flow of information from an intercepted Enigma message<ref>{{Citation |last=Sale |first=Tony |author-link=Tony Sale |title=Information flow from German ciphers to Intelligence to Allied commanders. |url=http://www.codesandciphers.org.uk/virtualbp/infoflow/infoflowie.htm |access-date=30 June 2011 |archive-url=https://web.archive.org/web/20110927061028/http://www.codesandciphers.org.uk/virtualbp/infoflow/infoflowie.htm |archive-date=27 September 2011 |url-status=live}}</ref>]]

The first personnel of the [[Government Code and Cypher School]] (GC&CS) moved to Bletchley Park on 15 August 1939. The Naval, Military, and Air Sections were on the ground floor of the mansion, together with a telephone exchange, teleprinter room, kitchen, and dining room; the top floor was allocated to [[MI6]]. Construction of the wooden huts began in late 1939, and Elmers School, a neighbouring boys' boarding school in a Victorian Gothic redbrick building by a church, was acquired for the Commercial and Diplomatic Sections.<ref>{{Harvnb|Smith|1999|pp=2{{ndash}}3}}</ref>

The only direct enemy damage to the site was done 20{{ndash}}21 November 1940 by three bombs probably intended for [[Bletchley railway station]]; Hut&nbsp;4, shifted two feet off its foundation, was winched back into place as work inside continued.<ref>{{Citation |last=Bletchley Park National Codes Centre |title=The Cafe in Hut 4 |url=http://www.bletchleypark.org.uk/content//index.rhtm |access-date=3 April 2011 |archive-url=https://web.archive.org/web/20130119043409/http://www.bletchleypark.org.uk/content//index.rhtm |archive-date=19 January 2013 |url-status=live}}</ref>

===Action This Day===
{{main|Action This Day (memo)}}
During a morale-boosting visit on 9 September 1941, [[Winston Churchill]] reportedly remarked to Denniston or Menzies: "I told you to leave no stone unturned to get staff, but I had no idea you had taken me so literally."<ref>{{Harvnb|Kahn1991|p=185}}</ref> Six weeks later, having failed to get sufficient typing and unskilled staff to achieve the productivity that was possible, Turing, Welchman, Alexander and Milner-Barry wrote directly to Churchill. His response was "Action this day make sure they have all they want on extreme priority and report to me that this has been done."<ref>{{Harvnb|Copeland|2004|page=336}}</ref>

===Allied involvement===
After the [[United States]] joined World War II, a number of American [[cryptographer]]s were posted to [[Hut 3]], and from May 1943 onwards there was close co-operation between British and American intelligence<ref>{{Harvnb|Taylor|1993|pp=71, 72}}</ref> leading to the [[1943 BRUSA Agreement]] which was the forerunner of the [[Five Eyes]] partnership.<ref>{{Cite news |title=Diary reveals birth of secret UK-US spy pact that grew into Five Eyes |last=Corera |first=Gordon |website=BBC News |date=5 March 2021 |url=https://www.bbc.co.uk/news/uk-56284453 |access-date=5 March 2021 |archive-date=5 March 2021 |archive-url=https://web.archive.org/web/20210305085038/https://www.bbc.co.uk/news/uk-56284453 |url-status=live }}</ref>

In contrast, the [[Soviet Union]] was never officially told of Bletchley Park and its activities, a reflection of Churchill's distrust of the Soviets even during the US-UK-USSR alliance imposed by the Nazi threat.<ref>{{cite book|url=https://books.google.com/books?id=8ZJxDwAAQBAJ&q=Churchill+distrust+Soviet+Union+bletchley&pg=PA571|title=The Concise Encyclopedia of World War II|page=571|first= Cathal J. |last=Nolan|publisher=Greenwood Press|year=2010|volume=1|isbn=978-0313330506}}</ref> However Bletchley Park was infiltrated by the Soviet mole [[John Cairncross]], a member of the [[Cambridge Spy Ring]], who leaked Ultra material to Moscow.{{sfn|Smith|2015|pp=81-82}}

===Postwar===
After the War, the secrecy imposed on Bletchley staff remained in force, so that most relatives never knew more than that a child, spouse, or parent had done some kind of secret war work.<ref>{{Harvnb|Hill|2004|pp=129{{ndash}}35}}</ref> Churchill referred to the Bletchley staff as "the geese who laid the golden eggs and never cackled".<ref>{{Harvnb|Lewin|2001|p=64}}</ref> That said, occasional mentions of the work performed at Bletchley Park slipped the censor's net and appeared in print.<ref>{{Harvnb|Thirsk|2008|pp=61–68}}</ref>

The site passed through a succession of hands and saw a number of uses, including as a teacher-training college and local [[General Post Office|GPO]] headquarters. By 1991, the site was nearly empty and the buildings were at risk of demolition for redevelopment,<ref>{{cite web|url=https://bletchleypark.org.uk/our-story/why-it-matters/preserving-bletchley-park|title=Preserving Bletchley Park|publisher=Bletchley Park|access-date=13 October 2018|archive-date=13 October 2018|archive-url=https://web.archive.org/web/20181013132927/https://bletchleypark.org.uk/our-story/why-it-matters/preserving-bletchley-park|url-status=dead}}</ref> before the gradual development of the [[Bletchley Park Museum]].<ref>{{cite web|url=https://bletchleypark.org.uk/|title=Welcome|publisher=Bletchley Park|access-date=13 October 2018}}</ref>

The Government Code & Cypher School became the Government Communications Headquarters (GCHQ), moving to [[Eastcote]] in 1946 and to [[Cheltenham]] in the 1950s.<ref>{{Citation |last= GCHQ |author-link= Government Communications Headquarters |title= Bletchley Park - post-war |year= 2016 |url= https://www.gchq.gov.uk/features/bletchley-park-post-war |access-date= 12 October 2018 |archive-date= 13 October 2018 |archive-url= https://web.archive.org/web/20181013053800/https://www.gchq.gov.uk/features/bletchley-park-post-war |url-status= dead }}</ref> The site was used by various government agencies, including the [[General Post Office|GPO]] and the [[Civil Aviation Authority]]. One large building, block F, was demolished in 1987 by which time the site was being run down with tenants leaving.<ref>{{cite web|url=https://www.pastscape.org.uk/hob.aspx?hob_id=1525325|title=Block F, Bletchley Park|publisher=Pastscape|access-date=12 May 2020}}</ref>