With one Oscar already under his belt, he became the first black actor since Sidney Poitier to win a coveted Best Actor Oscar…He’s not holding out for a hat-trick with British director Tony Scott’s latest blockbuster, but something tells Elaine Lipworth he has other things on his mind

With a pair of Oscar statuettes gracing his Los Angeles home, and regular multi-million pound pay cheques, Denzel Washington isn’t a man who is easily impressed. But a recent phone call from Harvard neurologist Dr Allen Counter did stir his interest.

The professor was calling to ask if Washington would host the Nobel Peace Prize Concert in Oslo on December 11, a clear indication of how he’s now regarded as one of the new elite of philanthropic Hollywood heavyweights, who are equally at home in the White House as they are on the red carpet.

Washington certainly moves in impressive social circles. Archbishop Desmond Tutu officiated when he and his wife renewed their marriage vows in 1995 in South Africa, and he played a prominent role in the inaugural celebrations for President Obama early last year, while his work with the Nelson Mandela Children’s Fund means he knows South Africa’s former president well enough to host him for dinner.

‘When Mr Mandela came to California he said, “I want to come to your house and eat with you.” So my wife made some chicken and we invited friends like Oprah Winfrey over.

‘He’s like the grandfather I never had – sitting in the living room telling stories. My children invited their close friends to meet him so they got to talk with him and take pictures. He’s so normal and wanted to be treated that way, and he was – apart from the helicopters flying around outside and the security everywhere.’

We’re sitting at either end of a green velvet sofa in an art deco suite at the Casa del Mar hotel on the beachfront in Santa Monica. He’s an imposing presence – 6ft tall – and I’m conscious of how toned he is. A strict regime of weights, boxing and swimming is obviously keeping middle age at bay. Washington’s films have grossed a staggering $3 billion worldwide, and include such blockbusters as The Pelican Brief, Crimson Tide and American Gangster.

But he’s also known for his performances in groundbreaking dramas that have earned him five Oscar nominations – a record for an African American actor (held jointly with Morgan Freeman). And he has tackled controversial subjects – notably in Richard Attenborough’s Cry Freedom, where he played South African anti-apartheid leader Steve Biko; Malcolm X, Spike Lee’s biopic about the assassinated black activist; and Philadelphia, which dealt with Aids.

At 55, the only clue as to his age is a distinguished smattering of grey in his hair. He’s a devout Christian (‘I read the Bible every day – the Book of Joshua absolutely inspires me’) and family-focused but deeply uncomfortable talking about himself.

His new film, Unstoppable, out on November 24, is directed by his British friend Tony Scott (brother of Ridley). It’s a thrilling rollercoaster ride in which his character attempts to stop an unmanned runaway train.

‘During the stunts we were running from carriage to carriage on top of a fast-moving train,’ says Washington.

‘In one scene we go backwards to catch up with the runaway train, and I climb up on top of a carriage and jump down between cars to turn on the manual brakes and slow it down. I was connected to a wire, but you can still fall off the side of the train at any moment.

‘The camera guys are on top, but they’re sitting down with a safety rail around them and they’re strapped on, while I’m having to run and there are helicopters buzzing all around your head. The director says it’s safe – “Oh, the wire will hold you if you stumble” – but the wire is loose, and I could still fall off the side or a passing tree or branch could hit me.’

He starts swaying in his seat, arms flailing, to illustrate his point.

‘People are flying through windows; they crash real trains, they blow trains up. And you don’t realise how tall a train is. You’re way up there and it’s not a smooth ride. It jerks all the time and the cars rattle and so at that moment it doesn’t matter how much money you’re making, if you fall off that train going 50 miles an hour you’re in big trouble.’

Things were made worse, the actor confesses, by the fact that in recent years he has begun to suffer from vertigo.

‘When I was younger I was never afraid of heights, but I’ve developed a fear. If I go out on a balcony I’ll get queasy. Flying on planes doesn’t bother me, but when the space is open and I can feel the air, it’s really hard. I have to make myself go out and look around for a while.

‘What bothers me most is people walking around me – maybe the fear of someone coming behind you and pushing you. So when I’m on the set with the crew and they’re getting the scene ready, I’ll tell them to finish their work and then I’ll come up and do my job.’