RAF Eastcote RAF Eastcote , also known over time as RAF Lime Grove , HMS Pembroke V and Outstation Eastcote , was a Ministry of Defence site in Eastcote , within the London Borough of Hillingdon . The British Government first used the site during the Second World War , constructing a military hospital in preparation for casualties from the D - Day landings . They were not required for the purpose and later became an outstation of the Bletchley Park codebreaking operations . During this time , Royal Air Force technicians and Navy Wrens supported the operations . The outstation closed soon after the end of the war , though became the first headquarters of Government Communications Headquarters ( GCHQ ) , when the Bletchley Park codebreaking operations were moved there and renamed in 1946 . These remained at Eastcote until 1954 when the new agency moved to its purpose - built headquarters in Cheltenham . Other buildings on the site were used by the General Post Office and to support the United States Air Forces in Europe ' s ( USAFE ) Third Air Force and 7th Air Division ( SAC ) activities at RAF South Ruislip . As part of the Ministry of Defence ' s Project MoDEL , the site became surplus to military requirements and was sold in 2007 to be redeveloped for new housing . The site was cleared in 2008 and a total of 385 new homes were approved for construction . The name for the development , Pembroke Park , was chosen to reflect the heritage of the site . History . Before coming under the ownership of the British Government , the land the site was built on was mainly open fields . A public footpath dating from around 1565 crossed the area from Eastcote High Road to Field End Road . In 1911 , cricket matches were played on the field by the Eastcote Institute . During the Second World War , the land was requisitioned by the Government from the owners , Telling Brothers . The first buildings on the site were constructed for use as a military hospital in preparation for military casualties from the Normandy landings . Subsequently , it became clear they would not be required for that purpose and became barracks for Navy Wrens . Bletchley Park established an outpost at the Eastcote site , known during the Second World War as HMS Pembroke V , to house some of the Bombe and Colossus codebreaker machines used to decode German Enigma messages . A total of 100 machines were operated at Eastcote , controlled by 800 Wrens and 100 RAF technicians . A detachment of American personnel were stationed in a separate area , operating their own Bombe machines . The site was split into two blocks : A and B . Block A was sited near Lime Grove and housed personnel accommodation and administrative services , while Block B was protected by brick walls and military police since it contained the codebreaking computers . The public footpath passed between the two blocks . The level of security meant that support staff in the administrative block did not know of the activities in Block B , nor did local residents . At the end of the war in 1945 , the Bombes were dismantled by the Wrens to be recycled , maintaining the secrecy of the operations . The operations at Bletchley Park under the name " Government Code and Cypher School " ( GCCS ) moved to Eastcote on 1 April 1946 . The Crown purchased the estate in 1947 . Eastcote ' s proximity to Whitehall meant staff were not far from London , and the site became known as the " London Signals Intelligence Centre " . Six years later , in July 1952 , GCCS became " Government Communications Headquarters " ( GCHQ ) and began to move from Eastcote to new purpose - built buildings in Cheltenham . The move was completed in February 1954 . Aside from the GCCS operations , the General Post Office ( GPO ) established a training school , and a women ' s teacher training college was opened in 1948 . The Ministry of Aviation also opened the Navaid training school on part of the site . The GPO had blocks built in the south - east area of the site , and other blocks were adapted from their original conditions for new uses . The CTS division of GCHQ remained on the site within Blocks C and D until 1987 . Aerial masts which had been erected by the division became unusable after the nearby train line was electrified , and were removed the year CTS left . In 1949 the United States Air Force established a non - flying base at RAF South Ruislip to coordinate the USAFE ' s Third Air Force and 7th Air Division ( SAC ) activities in Great Britain with the British Government . A school for the children of American service personnel was established on the Eastcote site in the 1950s . In the 1960s , this was joined by veterinary , dental , and mental health clinics , and also by a morgue . The United States military continued to use buildings on the site until the closure in 2007 . Redevelopment . The site was the first to be sold as part of the Ministry of Defence ' s Project MoDEL ( Ministry of Defence Estates London ) , a programme to reduce the number of military sites in the Greater London area . George Wimpey purchased the site in 2007 , planning to build 385 new homes . The entire site was cleared in 2008 and building commenced . George Wimpey became Taylor Wimpey through a corporate merger and submitted an application in 2010 to build a further 15 homes on the site . A report by the London Borough of Hillingdon ' s planning department rejected the proposal in December that year on the grounds that the site was already overdeveloped . Local residents had raised this concern in November that year , which the leader of the council explained was out of the council ' s control due to planning laws . As of May 2011 the new development has not been completed entirely , although residents began to move into the first of the newly built houses in December 2009 . The development has been named " Pembroke Park " in recognition of the heritage of the site ; roads and the play area also received names related to the wartime codebreaking that went on there .