In 1985, Cathy Massiter, an MI5 officer who had been responsible for the surveillance of CND from 1981 to 1983, resigned and made disclosures to a Channel 4 20 / 20 Vision programme, " MI5's Official Secrets ".

Peter Wright, former senior MI5 officer, said in his 1987 book that Litzi Friedmann was " almost certainly the person who recruited him to the Soviet cause.

Under interrogation by MI5 officer William Skardon at an informal meeting in December 1949, Fuchs initially denied being a spy and was not detained.

But after he passed an MI5 security check conducted by two MI5 officers ( Cyril Mills and Tomás Harris ) and an MI6 officer ( Desmond Bristow ), Mills ( who Pujol only ever knew as Mr Grey ) suggested that his code name be changed to, after Greta Garbo.

Pujol's MI5 case officer Tomas ( Tommy ) Harris

MI5 decided to use him against the Germans and assigned Ronnie Reed as his case officer.

An MI5 officer wrote in an assessment ' the Germans came to love Chapman ... but although he went cynically through all the forms, he did not reciprocate.

Former MI5 officer Peter Wright claimed in his memoirs, Spycatcher, that 30 MI5 agents then collaborated in an attempt to undermine Wilson.

Ronnie Reed, who ran double agents during the Second World War, and was an MI5 officer from 1940 to 1976, lived in Court Lane Gardens from 1960-1995.

This was a system based on an internal memo drafted by an MI5 officer in 1936, which criticised the long-standing policy of arresting and sending to trial all enemy agents discovered by MI5.

* Michael Bettaney, a former MI5 intelligence officer convicted of Official Secrets offences in 1984

* Anthony Blunt ( cryptonym: Johnson ), MI5 officer and Soviet agent

* Robert Hendy-Freegard, who posed as an MI5 officer.

An MI5 officer and friend of Philby from his earlier MI6 days, John Nicholas Rede Elliott was sent in 1963 to interview him in Beirut and reported that Philby seemed to know he was coming ( indicating the presence of yet another mole ).

MI5 officer John Preston, who was exploring hard left infiltration of the Labour party, investigates the stolen documents and finds that they were leaked by George Berenson, a passionate anti-communist and supporter of South Africa.

David Shayler ( born 24 December 1965 ) is a British journalist and former MI5 ( Security Service ) officer.

He later attended the University of Dundee starting in 1984 where he was editor of the student newspaper Annasach and was responsible for publishing extracts of the book Spycatcher by another former MI5 officer Peter Wright ( banned in England at the time ).

* Peter Wright, a former MI5 counterintelligence officer, Spycatcher author

Its most audacious investigation of the intelligence community was perhaps an extended edition in July 1984 titled " The Spy Who Never Was ", the confessions of a former MI5 officer, Peter Wright.

The total would have been higher had not William Joyce been tipped off by an MI5 officer ( probably Charles Maxwell-Knight ) of his impending internment, allowing him to flee to Germany.

In 1963, American writer Michael Straight, also an Apostle, and later publisher of The New Republic magazine, admitted to a covert relationship with the Soviets, and he named Anthony Blunt, MI5 officer, director of the Courtauld Institute, and art adviser to the Queen as his recruiter and a Soviet spy.

My Father, The Man Who Never Was: Ronnie Reed, The Life and Times of an MI5 Officer.

This was MI5 Officer Ronnie Reed, who was also Case Officer for Agent Zigzag.

In February 2012 an MI5 file on Chaplin was opened to the public which revealed that the FBI had contacted the British secret service to provide them with information which would enable them to ban Chaplin from the US.

This much had already been confirmed by former cabinet secretary Lord Hunt, who concluded in a secret inquiry conducted in 1996 that " there is absolutely no doubt at all that a few, a very few, malcontents in MI5 ... a lot of them like Peter Wright who were rightwing, malicious and had serious personal grudges – gave vent to these and spread damaging malicious stories about that Labour government.

There, he underwent MI5 interrogation aimed at ascertaining whether he had acted as a " third man " in Burgess and Maclean's spy ring.

The head of MI6, Dick White, only recently transferred from MI5, had suspected Philby as the " third man.

MI5, with advance warning of infiltration, had no trouble picking up all of the spies sent to the country.

The experiment had not appeared to be a success, but MI5 had learned key lessons about how the Abwehr operated and how double agents might be useful.

Robertson's first agents were not a success ; Giraffe ( George Graf ) was never really used and Gander ( Kurt Goose ; MI5 had a thing for amusingly relevant code names ) had been sent to Britain with a radio that could only transmit, not receive.

Thanks to Ultra, MI5 had prior knowledge of his mission.

( Reed had been invited to join MI5 in 1940 and remained until his retirement in 1976 ).

Chapman was given a £ 6, 000 payment from MI5 and was allowed to keep £ 1, 000 of the money the Germans had given him.

Bennett had free and unfettered access to the archives of the Foreign Office as well as those of the Secret Intelligence Service ( SIS ), MI5, and MI6.

In March 1987, James Miller, a former agent, claimed that the Ulster Workers Council Strike of 1974 had been promoted by MI5 in order to help destabilise Wilson's government.

In 2009, Defence of the Realm, the authorised history of MI5 by Christopher Andrew, held that while MI5 kept a file on Wilson from 1945, when he became an MP – because communist civil servants claimed that he had similar political sympathies – there was no bugging of his home or office, and no conspiracy against him.

The Germans had about 50 agents in England at the time, but B1A ( the Counter-Intelligence Division of MI5 ) had caught all but one of them ( he died in unclear circumstances ).

Britain's internal security service, MI5, had signed up two sources inside the branch to hand over copies of all documents relating to Abu Nidal's accounts.

But the play also explores the involvement of MI5 and the troubled relationship between Macmillan and his wife Dorothy ( Clare Higgins ) who had made no secret of her adultery with the wayward Tory MP, Robert Boothby.

* In 2003, the Pakistani embassy building in London was found bugged ; contractors hired by MI5 had planted bugs in the building in 2001.

According to the official history of MI5, the actual number of agents identified was 22 and Kell had started sending out letters to local police forces on 29 July giving them advance warning of arrests to be made as soon as war was declared.

Thus by the end of the war, MI5 was a fully-fledged investigating force ( although it never had the powers of arrest ), in addition to being a counter-espionage agency.