Anthony Blunt, who worked at Buckingham Palace as Surveyor of the Queen’s Pictures, was secretly a Soviet spy during WWII.

Queen Elizabeth II was not officially informed for almost a decade that one of her most senior courtiers had confessed to being a Soviet spy, according to newly released MI5 files.

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

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.

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.

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

Newly released MI5 files from the National Archives reveal that British intelligence monitored potential connections between French government interests and nationalist movements in Scotland and Wales during the 1960s.

The manual gives instructions on preferred appearances, disguises and how to follow targets – but warns against fake moustaches

Avoid false beards, carry plenty of spare change and know what to do when you need to tell a taxi driver "follow that cab!" - these were some of the tips given to rookie MI5 "watchers".

MI5 feared film star Dirk Bogarde could be the target of a KGB gay "entrapment" attempt after it emerged he was on a list of 'six practising British homosexuals' passed to the Russians

A newly declassified document is on display at the National Archives. It reveals the advice given to new MI5 recruits during the Second World War.

The files about royal art historian Anthony Blunt are among a trove from the intelligence agency MI5 released Tuesday by Britain’s National Archives.