The agent behind the 'Argo' mask

"If you were to ask me was it as good as Tom Cruise" - in the Mission: Impossible movies - "I would say every bit. But Tom Cruise requires about five hours to get ready. We had to do it in five seconds, with no retakes."

The former CIA technical officer estimates that the one meeting in Laos saved the United States $4 billion. About 85 per cent of the key intelligence questions the CIA raised about the Soviet Union and its weapons development were answered in South Asia as a result of the agency's work there, he says, as the Soviets sold their weapons to communist governments in the region. "We were mining high-grade ore."

For his CIA job Mendez needed skills similar to those of a creative artist working in Hollywood, but he never considered leaving the agency - and pretending to be a film producer didn't whet his appetite to work in movies, either. "I was having too much fun," he says.

To create foolproof disguises, Mendez says you need basic hand skills and a knowledge of chemistry. "You have to have to a thirst for knowledge about the world, because what you are doing as a master of disguise is creating scenarios around the world that allow you to come and go, and not compromise your assets. So hand skills, the ability to travel, observe and create things are necessary," he says. "You also have to be a romantic, because you can't tell anybody what you have done, so you have to get your approval from within."

Mendez says that recognising new threats is always a problem for intelligence services. The Iranian hostage crisis showed that the "rules of engagement were different". "There were no rules, in fact, only a vicious, rabid contingent of people who were unpredictable: they are not going to the negotiating table; they are going to blow up the table."

For the Iranian exfiltration, Mendez says he chose the guise of an Irish film producer because the Irish blend in. He also has Irish blood in him from his roots in Nevada, so this seemed a perfect alter ego.

"As you know, the Irish are ubiquitous around the world. What you want to do is use some cover legend that puts you in a large population so you can blend in. The Irish are nonthreatening," he says. "The Irish are sort of charming, you know - you want to be a friendly face. They are always ready to tell you a good story, and we made up some good stories."

During the fake film-scouting mission to Tehran, locals were more interested in his Hollywood connections than in his Irish identity, despite a well-practised Irish accent, which he says was "a bit of all right".

"I have been working on it for years - that is why I hang out in pubs. I listened to very many recordings. I drank a lot of pints of Guinness."