Q WHAT is the difference between MI5 and MI6, and were spies such as Guy Burgess and Anthony Blunt members of these organisations? - J Anderson, Houghton-le-Spring.

A MI5 and MI6 are British security intelligence services and agencies of the British government. MI5 is concerned with internal security and domestic counter-intelligence while MI6 is concerned with foreign intelligence.

MI5 and MI6 were sections of the Secret Service Bureau formed in 1909 from the recommendations of the Committee of Imperial Defence. Their initial remit was to identify and prevent the activities of German spies. They were particularly concerned with the threat of German spies in British naval ports.

From 1916 the bureau became part of a Directorate of Military Intelligence (hence the letters MI) and the titles MI5 and MI6 came to be used. At the outbreak of the Second World War, MI5's staff were located in Wormwood Scrubs Prison before moving to Blenheim Palace in Oxfordshire - the birthplace and ancestral home of Winston Churchill.

During the war, the use of double agents played a big part in counteracting the work of German military spies. False information was fed to German intelligence and this helped significantly in the success of the Normandy landings.

Throughout the 1950s the activities of MI5 and MI6 were focused on the Soviet Union and the service detected a number of British double agents working for the Soviets. The names of these spies are now well known - Guy Burgess, Donald McLean, Kim Philby and Anthony Blunt.

Burgess was a member of MI6 and was also a BBC correspondent, and member of the Foreign Office from 1944. Perhaps more dangerous was McLean, a colleague of Burgess at the Foreign Office. He became the Head of the Chancery at the British Embassy in Washington DC, where Burgess was also employed for a time. McLean became secretary of the Combined Policy Committee on Atomic Development and had access to highly privileged information. British intelligence services were closing in on these two figures in 1951 but the spies were tipped off and escaped to the Soviet Union where they were joined later by a third double agent, Kim Philby, in 1963. The fourth member of this team who had assisted in their escape was Sir Anthony Blunt. The activities of Blunt were discovered in 1964, but his name was not revealed until 1979.

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