Rookie wartime MI5 "watchers" were advised they needed to be prepared to offer a big tip if they had to tell a taxi driver to "follow that cab" when pursuing a suspect, newly declassified documents reveal.

The newly-declassified documents include details about some of the UK's most notorious spies.

A World War II-era tailing guide is among declassified records shedding light on spy game in MI5: Official Secrets, at the National Archives.

Despite advances in electronic surveillance, security service MI5 still relies on human ‘watchers’. Government documents reveal what it takes to follow suspects without being detected.

Top secret MI5 files detailing first-hand accounts of confessions of three of Britain's most notorious double agents including Kim Philby and Anthony Blunt who spied for the Soviet Union were released for the first time on Tuesday.

Recently released MI5 files reveal confessions from Britain's notorious double agents, including Kim Philby and Anthony Blunt, who spied for the Soviets. These declassified documents, made public by the National Archives,

MI5 reveals confessions of three members of infamous Cambridge Five spy ring as tranche of documents released into National Archives

The guidance will feature in a new exhibition at the National Archives focusing on the work of the Security Service.

These instructions, part of a declassified training booklet for rookie operatives, are now on display at the National Archives in Kew, west London, as part of a new exhibition on MI5’s wartime ...

Historian and exhibition curator Mark Dunton speaks about special files that will form part of a special exhibition at the National Archives titled 'MI5: Official Secrets', featuring case files used by spies in the agency's 115-year history.

The National Archives said this was the first time in the intelligence agency's 115-year history that it had been a partner in such an exhibition. Unlike other government departments, MI5 is not ...