Noriega plays Txema, a Basque construction worker facing bankruptcy who is persuaded by the Spanish special forces to infiltrate the terrorist organisation. His codename: El Lobo (the wolf).

Set in the Seventies during the last gasp of the Franco regime, the film is based on a true story — El Lobo himself is still alive and living under an assumed identity with a new face.

The film bears certain similarities, in its conflicts of interest and muddled personal identities, to the 1997 Mafia sting movie Donnie Brasco. And the parallels don’t stop there. Like that film’s star, Johnny Depp, Noriega is an actor saddled with a rather limiting heart-throb tag. By seeking out more complex, adult roles he has earned a newfound respect for his abilities. El Lobo, says Noriega, was a turning point in his career. Until then, in films such as Alejandro Amenábar’s Tesis and Open Your Eyes, he had focused on hip cinema for a younger audiences. “But with Lobo there were so many people who saw the film. Sixty-year-olds stopped me and said: ‘You are Lobo, well done’.”

A taut, atmospheric thriller that prickles with paranoia and distrust, El Lobo is the story of a young man’s ideological awakening. Txema is at first more concerned with supporting his wife and child than he is with the struggle for Basque independence. His undercover work is part of a police operation designed to neutralise the terrorist cells using any means necessary.

But as he rises through the ranks of Eta, Txema begins to believe that he could bring about a peaceful solution by persuading his cohorts to disarm and continue their battle with more legitimate political means. It’s at this moment that both the police and his Eta comrades turn against him.

The fact that El Lobo is based on a real character is something that weighed heavily on Noriega. “I always feel the responsibility when I am working. It is going to be for ever. I take my job really seriously. But when it’s a real character, it’s bigger. It’s a weird feeling knowing that someone is going to look at it and ask, is that me?” Noriega chose not to meet the subject of the film before shooting, relying instead on books and documentaries for research.

However, he later met the real El Lobo, who is still in hiding and wears gloves (“because he says Eta can recognise you by your hands”). The man he met was someone desperate for acknowledgment. “He was really proud and happy with the film — finally, people are going to recognise what he did. After 30 years hidden, the film was a way to show his face and say, this is me.”

In the flesh he was not quite what Noriega, who comes across as quite a serious, intense kind of a chap, had expected. “He was really excited about the idea of meeting me. I thought we were going to talk about Eta and important things. But he was like: ‘Ah, the girl in the film is amazing but you should have seen the girls I had in that time.’ He was excited like a little boy.”

So what drew the Spanish public to this film when others that dealt with Eta had been either ignored, or, as in the case of Julio Medem’s admittedly unbalanced documentary The Basque Ball, the cause of protests? Noriega muses: “Eta was in the news every day, so why would people want to go and see a film about Eta? But one important thing is that this was 30 years ago. You can talk about it with distance. It was not something that we suffered yesterday.”

Noriega has retained a political theme with his latest project, Che Guevara, a lowbudget American production directed by Josh Evans (son of the producer Robert Evans and actress Ali MacGraw). The Spaniard plays the title role, while Fidel Castro is played by the Italian actor Enrico Lo Verso, who, ironically, is so violently allergic to cigars that he can’t even touch them.

“If I felt responsibility doing Lobo,” says Noriega, “imagine what I felt doing Che Guevara. The problem with Che is that now, he’s everywhere in the world. He’s a symbol, a myth. He’s a symbol of so many things but not necessarily true things. Everybody thinks that they know Che Guevara but not so many people really know the story. I didn’t want to play the poster, I wanted to play the man.”

El Lobo is released on June 15

Assassins for hire: actors who played terrorists

Nicolas Cage played terrorist for hire Castor Troy in the ludicrous but rather entertaining Face/Off (1997).

Gary Oldman employed his trademark shifty look as a Russian terrorist who hijacks the US President’s plane in Air Force One (1997).

Ayesha Dharker played a Tamil suicide bomber in Santosh Sivan’s striking film The Terrorist (1999). She later appeared in Star Wars: Episode II.

James Mason was a wounded IRA terrorist forced to hide out in Belfast in Carol Reed’s Odd Man Out (1947).

Explore Film

• Film Reviews

• DVD

• Oscars

• Bollywood

Editor's choice

• The top 10 fan versus band scuffles
• Mamma Mia! The first review
• Times critics' 20 best films for kids