Damian in the dark about his big role

Damian Lewis has been up since 7am, but is on remarkably fine form – and has an admission to make.

“You need to know I’m in my pyjamas, clasping a coffee,” he reveals, chuckling down the phone from America, where the working day’s just starting.

The London native, best known for being in The Forsyte Saga, Band Of Brothers and Life, has made North Carolina his temporary home for the past five months to film new US TV series Homeland.

In doing so Lewis has made the ultimate sacrifice – being apart from his family, actress wife Helen McCrory and their two children, five-year-old daughter Manon and son Gulliver, four.

“North Carolina is a beautiful place and I like it here a lot. But I miss my family when they’re not here with me, although they were with me all summer,” he admits in his clipped Old Etonian accent.

“I also miss London because I love London – it is the greatest city in the world. I miss the culture, the vibrancy and bombing around on my bicycle from one place to the next.”

Homeland, the Golden Globe-winning psychological thriller, which also stars Claire Danes and fellow Brit David Harewood MBE, was created by Howard Gordon and Alex Gansa – the brains behind 24.

“The parallel with 24 is inevitable, but this is far more of a psychological, political drama. It’s something we don’t see often – plus you need a black man and a redhead on a show!” he quips.

Lewis, pictured, plays US Marine Sergeant Nicholas Brody, who has been held as a prisoner of war for eight years by Al Qaeda and presumed dead.

He is celebrated as a war hero on his return, but mentally unstable CIA agent Carrie Mathison (Danes) suspects he has been ‘turned’ into a sleeper agent and is now a threat to Homeland security.

“Ambiguity is a complex thing to play. You have to be lightning quick and nimble, there’s a mental and imaginative agility in the performance which is really fun,” says Lewis, 41.

“Inserting a bipolar disorder into the heart of a paranoid thriller is a brave move, as it conveniently allows us to judge Carrie. Is this man a danger to the United States or is she over-reacting? It’s intense. You’re going to love it!”

The series, which has been renewed for a second season, already has famous fans, with US President Barack Obama and his cohorts reported to have called in four DVD box sets.

“It’s exciting when you’ve entered the cultural zeitgeist in such a way,” says Lewis, who last worked in the US on the short-lived NBC cop drama Life.

“The Clintons are now watching it, and it’s gone right through to the top levels of the American administration. They’re all asking for box sets so they can see what their bosses are watching.”

But it could all have turned out differently as Lewis admits: “I very nearly said no to Homeland.

“My experience on Life, which I loved, was at quite a lot of personal cost, from a family point of view. That sounds a bit melodramatic - we’re all still together - but it was long hours working, with Helen sitting in the house with the kids.

“I wasn’t prepared for quite the workshop hours you work on some American TV shows, so I said to my agent I would do this only if it’s extraordinary and is on cable TV.”

The actor particularly enjoys his scenes with Romeo And Juliet actress Danes. “Danesy is whip-smart, extremely committed and focused. She plays that interactive Scrabble game, Words With Friends, endlessly.

“She has about five or six games going on with different people, and got half the crew doing it as well. It’s her way of relaxing.”

Like the audience, Lewis is kept in the dark about his character’s plotlines. “The fundamentals of my character were discussed but the details weren’t fleshed out,” he says.

“It’s fun getting surprises with the episode each week, like reading a novel. It keeps it fresh and interesting.”

The British actor - who attended the Guildhall School of Music and Drama and performed with the Royal Shakespeare Company - did what little research he could.

“I spoke to soldiers, read a lot of literature, looked at documentary footage and tried to understand what it is like to be held as a prisoner of war.

To be authentic in its portrayal of Afghanistan prisons, Lewis had to endure routine torture scenes in which he was stripped of his clothes and subjected to gruelling punishment.

The scenes don’t affect him though, and he jokes: “It leaves me needing a beer! I don’t take my work home with me. I’m not that kind of method actor.

Lewis seems content with his lot, but there’s one person he’d gladly switch places with - Jon Hamm of Mad Men fame.

“I wish I had got the Don Draper role. I’ve got a little bit of a man crush on him!” he laughs.