If this information had surfaced during the war, however, it could have caused a bit of a sticky wicket.
A blunder by MI5 has blown the cover on some of its top wartime agents 60 years after they were recruited to carry out secret operations.
Despite a tradition of protecting the identities of spies, an apparently innocuous file released by MI5 to the National Archives has allowed a number of agents who operated during the Second World War to be identified.
The information is contained in a schedule from the body's secret wartime interrogation centre, Camp 020, in which captured German agents were interrogated and "broken".
Names and dates on the schedule can be cross checked against other files where the names of agents have been blacked out, allowing their identities to be confirmed.
The names include those of IRA members, Poles, Scandinavians and other foreigners trained in spy craft by the German intelligence services before being sent on missions to Britain.
Some stayed on in the UK after the war and at least one, a Pole, is thought to be still alive. Among the listed Irishmen is Joseph Lenihan, one of a number of agents whose identities had been the subject of much historical research.
Codenamed "Basket", Lenihan had first been recruited by German military intelligence before being "turned" by MI5.
Those named in the schedules were interrogated at Camp 020, based in Latchmere House in Middlesex, which was crucial in detecting German spies entering Britain and turning them into double agents.
A spokesman for MI5 said yesterday: "We neither confirm nor deny the identities of past or present MI5 agents."