Government Communications Headquarters The Government Communications Headquarters ( GCHQ ) is a British intelligence agency responsible for providing signals intelligence ( SIGINT ) and information assurance to the British government and armed forces . Based in Cheltenham , it operates under the guidance of the Joint Intelligence Committee . GCHQ was originally established after the First World War as the Government Code and Cypher School ( GC & CS or GCCS ) and it was known under that name until 1946 . During the Second World War it was located at Bletchley Park . GCHQ is the responsibility of the UK Secretary of State for Foreign and Commonwealth Affairs , but it is not a part of the Foreign Office and its Director ranks as a Permanent Secretary . In 2013 , GCHQ received considerable media attention when the whistleblower Edward Snowden revealed that the agency was attempting to collect all online and telephone data in the UK via the Tempora programme . The Communications - Electronics Security Group ( CESG ) is the branch of GCHQ working to secure the communications and information systems of the government and critical parts of British national infrastructure . The JTLS ( Joint Technical Language Service ) is a small department and cross - government resource responsible for mainly technical language support and translation and interpreting services across government departments . It is co - located with GCHQ for administrative purposes . Structure . GCHQ is led by the Director of GCHQ , currently Sir Iain Lobban , and a Corporate Board , made up of Executive and Non - Executive Directors . Reporting to the Corporate Board is : History . Government Code and Cypher School ( GC & CS ) . During the First World War , the United Kingdom ' s Army and Navy had separate signals intelligence agencies , MI1b and NID25 ( initially known as Room 40 ) respectively . In 1919 , the Cabinet ' s Secret Service Committee , chaired by Lord Curzon , recommended that a peace - time codebreaking agency should be created , a task given to the then - Director of Naval Intelligence , Hugh Sinclair . Sinclair merged staff from NID25 and MI1b into the new organisation , which initially consisted of around 25 – 30 officers and a similar number of clerical staff . It was titled the " Government Code and Cypher School " , a cover - name chosen by Victor Forbes of the Foreign Office . Alastair Denniston , who had been a member of NID25 , was appointed as its operational head . It was initially under the control of the Admiralty , and located in Watergate House , Adelphi , London . Its public function was " to advise as to the security of codes and cyphers used by all Government departments and to assist in their provision , " but also had a secret directive to " study the methods of cypher communications used by foreign powers . " GC & CS officially formed on 1 November 1919 , and produced its first decrypt on 19 October . Before the Second World War , GC & CS was a relatively small department . By 1922 , the main focus of GC & CS was on diplomatic traffic , with " no service traffic ever worth circulating " and so , at the initiative of Lord Curzon , it was transferred from the Admiralty to the Foreign Office . GC & CS came under the supervision of Hugh Sinclair , who by 1923 was both the Chief of SIS and Director of GC & CS . In 1925 , both organisations were co - located on different floors of Broadway Buildings , opposite St . James ' s Park . Messages decrypted by GC & CS were distributed in blue - jacketed files that became known as " BJs " . In the 1920s , GC & CS was successfully reading Soviet Union diplomatic ciphers . However , in May 1927 , during a row over clandestine Soviet support for the General Strike and the distribution of subversive propaganda , Prime Minister Stanley Baldwin made details from the decrypts public . During the Second World War , GC & CS was based largely at Bletchley Park in present - day Milton Keynes working on , most famously , the German Enigma machine and Lorenz ciphers , but also a large number of other systems . In 1940 , GC & CS was working on the diplomatic codes and ciphers of 26 countries , tackling over 150 diplomatic cryptosystems . Senior staff included Alastair Denniston , Oliver Strachey , Dilly Knox , John Tiltman , Edward Travis , Ernst Fetterlein , Josh Cooper , Donald Michie , Alan Turing , Max Newman , William Tutte , I . J . ( Jack ) Good , Peter Calvocoressi and Hugh Foss . An outstation in the Far East , the Far East Combined Bureau was set up in Hong Kong in 1935 , and moved to Singapore in 1939 . Subsequently with the Japanese advance down the Malay Peninsula , the Army and RAF codebreakers went to the Wireless Experimental Centre in Delhi , India . The Navy codebreakers in FECB went to Colombo , Ceylon , then to Kilindini , near Mombasa , Kenya . GC & CS was renamed the " Government Communications Headquarters " in June 1946 . Post Second World War . GCHQ was at first based in Eastcote , but in 1951 moved to the outskirts of Cheltenham , setting up two sites there – Oakley and Benhall . GCHQ had a very low profile in the media until 1983 when the trial of Geoffrey Prime , a KGB mole within GCHQ , created considerable media interest . Since the days of the Second World War , US and British intelligence have shared information . For the GCHQ this means that it shares information with , and gets information from , the National Security Agency ( NSA ) in the US . Public key encryption . Early in the 1970s , the asymmetric key algorithm was invented by staff member Clifford Cocks , a mathematics graduate . This fact was kept secret until 1997 . Trade union disputes . In 1984 , GCHQ was the centre of a political row when the Conservative government of Margaret Thatcher prohibited its employees from belonging to a trade union . It was claimed that joining a union would be in conflict with national security . A number of mass national one - day strikes were held to protest this decision , seen as a first step to wider bans on trade unions . Appeals to British Courts and European Commission of Human Rights were unsuccessful . The government offered a sum of money to each employee who agreed to give up their union membership . Appeal to the ILO resulted in a decision that government ' s actions were in violation of Freedom of Association and Protection of the Right to Organise Convention . The ban was eventually lifted by the incoming Labour government in 1997 , with the Government Communications Group of the Public and Commercial Services ( PCS ) Union being formed to represent interested employees at all grades . In 2000 , a group of 14 former GCHQ employees , who had been dismissed after refusing to give up their union membership , were offered re - employment , which three of them accepted . Post Cold War . Since 1994 , GCHQ activities have been subject to scrutiny by Parliament ' s Intelligence and Security Committee . Post - Cold War , the aims of GCHQ were set out by the Intelligence Services Act 1994 . At the end of 2003 , GCHQ moved to a new circular HQ ( popularly known as ' the Doughnut ' ) : at the time , it was the second - largest public - sector building project in Europe , with an estimated cost of £337 million . The new building , which was designed by Gensler and constructed by Carillion , is the base for all of GCHQ ' s Cheltenham operations . The public spotlight fell on GCHQ in late 2003 and early 2004 following the sacking of Katharine Gun after she leaked to " The Observer " a confidential email from agents at the American National Security Agency addressed to GCHQ agents about the wire - tapping of UN delegates in the run - up to the 2003 Iraq war . GCHQ gains its intelligence by monitoring a wide variety of communications and other electronic signals . For this , a number of stations have been established in the UK and overseas . The listening stations are at Cheltenham itself , Bude , Scarborough , Ascension Island , and with the United States at Menwith Hill . Ayios Nikolaos Station in Cyprus is run by the British Armed Forces for GCHQ . In March 2010 , GCHQ was criticised by the Intelligence and Security Committee for problems with its IT security practices and failing to meet its targets for work targeted against cyber attacks . Spying on foreign politicians at 2009 G - 20 London Summit . As revealed by Edward Snowden in " The Guardian " , GCHQ spied on foreign politicians visiting the 2009 G - 20 London Summit by eavesdropping phonecalls , emails and monitoring their computers , and in some cases even ongoing after the summit via keylogger s that had been installed during the summit . Some of the information gained has been passed on to British politicians . 2013 " Tempora " data collection . Documents leaked by former NSA contractor Edward Snowden in 2013 suggest that GCHQ operates a clandestine security electronic surveillance program named " Tempora " and has had access to the US internet monitoring programme PRISM since at least June 2010 . PRISM is said to give the National Security Agency and FBI easy access to the systems of nine of the world ' s top internet companies , including Google , Facebook , Microsoft , Apple , Yahoo and Skype . CESG . CESG ( originally Communications - Electronics Security Group ) is the group within GCHQ which provides assistance to government departments on their own communications security : CESG is the UK National Technical Authority for information assurance , including cryptography . CESG does not manufacture security equipment , but works with industry to ensure the availability of suitable products and services , while GCHQ itself can fund research into such areas , for example to the Centre for Quantum Computing at Oxford University and the Heilbronn Institute at the University of Bristol . CESG runs a number of schemes such as CHECK , CLAS , Commercial Product Assurance , and CESG Claims Tested Mark and CAPS . Joint Technical Language Service . The Joint Technical Language Service ( JTLS ) was established in 1955 , drawing on members of the small Ministry of Defence technical language team and others , initially to provide standard English translations for organisational expressions in any foreign language , discover the correct English equivalents of technical terms in foreign languages and discover the correct expansions of abbreviations in any language . The remit of the JTLS has expanded in the ensuing years to cover technical language support and interpreting and translation services across the UK Government and to local public sector services in Gloucestershire and surrounding counties . The JTLS also produces and publishes foreign language working aids under crown copyright and conducts research into machine translation and on - line dictionaries and glossaries . The JTLS is co - located with GCHQ for administrative purposes . International relationships . GCHQ operates in partnership with equivalent agencies worldwide in a number of bi - lateral and multi - lateral relationships . The principal of these is with the United States ( National Security Agency ) , Canada ( Communications Security Establishment ) , Australia ( Defence Signals Directorate ) and New Zealand ( Government Communications Security Bureau ) , through the mechanism of the UK - US Security Agreement , a broad intelligence sharing agreement encompassing a range of intelligence collection methods . Relationships are alleged to include shared collection methods , such as the system described in the popular media as ECHELON , as well as analysed product . Constitutional legal case . A controversial GCHQ case determined the scope of judicial review of prerogative powers ( the Crown ' s residual powers under common law ) . This was " Council of Civil Service Unions v Minister for the Civil Service " [ 1985 ] AC 374 ( often known simply as the " GCHQ case " ) . In this case , a prerogative Order in Council had been used by the prime minister ( who is the Minister for the Civil Service ) to ban trade union activities by civil servants working at GCHQ . This order was issued without consultation . The House of Lords had to decide whether this was reviewable by judicial review . It was held that executive action is not immune from judicial review simply because it uses powers derived from common law rather than statute ( thus the prerogative is reviewable ) . Controversially , they also held that although the failure to consult was unfair , this was overridden by concerns of national security . Leadership . The following is a list of the heads of the operational heads of GCHQ and GC & CS :