Confessions of double agents and tips for new spies have been released as part of a tranche of recently-declassified documents from MI5. The documents are part of a new exhibition on display at the National Archives this spring and include details about some of Britain's most notorious spies.

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

Do not use false beards, carry plenty of spare change for the tube, and if you have to tell a taxi driver to "follow that cab", be prepared to give him a big tip. That was the advice issued to rookie MI5 "watchers" whose job it was to covertly follow and report on suspected enemy agents.

The guidance is contained in a booklet for recruits during World War Two, which will go on display at the National Archives in Kew, west London 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,