Tom Hanks is five times the actor he used to be.

Thanks to new technology, he could play any number of roles in his Christmas movie, The Polar Express, in which an eight-year-old boy boards a train for a trip to see Santa Claus at the North Pole.

Chris Van Allsburg's book is one that Hanks read many times to his children.

He bought the rights and took the project to director Robert Zemeckis, with whom he worked on Forrest Gump and Castaway. They decided to use a new computer animation technique to turn the story into a movie, making it the first feature film to be shot entirely in "performance capture technology".

This enabled Hanks to play five roles, including the young hero, the conductor and Santa Claus.

Originally, when they had been considering a traditional live action film, he had only seen himself as the conductor. With the new technique he could play any role he wanted - or even every role if he desired.

"Bob Zemeckis said, 'You can play the kid' and that was really a light bulb going on. As soon as you're free from having kids in the movie, who essentially you have to trick to perform, it really became quite freeing," says Hanks.

"Because the book and the story of the movie is told in the first person by the boy, all the recollections come from his own brain and all the adults resemble his father. I believed those were the roles the boy created in his own head and, therefore, I could have a take on all those."

Five roles didn't mean he pocketed five pay cheques. "I just took my $300 a week and made it work somehow," he jokes. "We shot the whole thing in 35 days. It's not something I'm anxious to do again, not at that pace."

The actors, wearing special suits and covered in hundreds of sensors, performed their scenes without sets and props. Their performances were then transferred into the digitally-made film. The result looks like animation but the movements and emotions are based in reality

"As soon as you could imagine what you wanted to do, you could do it. You didn't wait for lighting or props or costumes to be adjusted," Hanks says.

"The only thing that took up time was if one of those special sensors that cost about three bucks apiece fell off our face. They had to find it and replace it or the computer was going to read your ear or your cheekbone down on the floor."

The process was different to voicing cowboy Woody in the Toy Story computer-animated movies.

"There, you go on a sound stage and read the lines in 17 different ways. They take the one they want and edit it all together. That's interesting to a degree, an art form and discipline in itself," he says.

"With The Polar Express we got to be actors. We didn't have costumes or props but the human interaction was as real as we could make it. We were pouring our guts out dressed as idiots, but we all felt like actors rather than recording artists."

Unlike the hero, Hanks would not have hesitated in jumping aboard the train at that young age. "In fact, I'd have been waiting for the train," he says, recalling how he was fearless as a youngster. "I moved around a lot as a kid and had no trepidation of being in a new place. I kind of enjoyed it.

"My house was an entertaining place as it was. We didn't have any real rules that we had to adhere to. I was used to pretty much calling my own shots."

His parents divorced when he was five, and afterwards he travelled around California with his father. He once described his upbringing as "three moms, five schools and ten homes".

Having to constantly settle into new surroundings with new people was good preparation for acting. "A lot of being an actor is having no self-consciousness in order to do something very artificial - to get out on stage and pretend to be somebody else," he says. "I wanted to be the guy who told the stories and moving around shook out any self-consciousness I would have had."

He is now one of the world's best liked, most successful movie stars, as well as the first in 50 years to win back-to-back Oscars for Philadelphia and Forrest Gump.

He does not possess obvious leading man looks but has proved equally adept at comedy and drama in Sleepless In Seattle, Saving Private Ryan, Apollo 13, A League Of Their Own, The Green Mile, Castaway and The Road To Perdition.

From a less-than-auspicious big screen debut in slasher movie He Knows You're Alone, he has gone on to notch up seven 100 million dollar-plus movies at the US box office. Money alone does not motivate him, although he has said that "if you have to have a job in the world, a high-price movie star is a pretty damned good gig".

However, his run of blockbusters was halted by this summer's release of the Coen Brothers' remake of The Ladykillers, with Hanks taking the Alec Guinness role, and Steven Spielberg's The Terminal. If he is worried that people will start claiming he has lost his appeal, he does not show it.

"You can't be a slave to the concept of box office," he says. "If I was I'd be doing Forrest Gump 5. I would be the richest, fattest, most bored actor on the planet Earth."

Updated: 10:01 Friday, December 10, 2004