It's a tribute to Paul Bettany's talent, his dedication to the cause and to the coaching of former champion Pat Cash that when you watch the English actor on court in Wimbledon you believe every move he makes, every shot he hits.

Because, remarkably, when 33-year-old Paul agreed to take the part he had never played tennis before in his life. "Never," he smiles. "Not ever.."

"I got married on New Year's Day," says Paul. "And I remember a week later I started training - on court and in the gym, to build up the physique. And I kind of thought well, this will be fun...' Little did I know what I was letting myself in for."

For six days a week for six months Bettany spent hours working out practicing tennis, in New York and at home in London. By the time filming started in the summer of 2003, Bettany was, according to Cash - who won the Wimbledon title in 1987 - in great shape and had mastered the game to an impressive level.

"Paul went from never really having played any sports to moving like an athlete and he looks really good around the net where it matters - diving, lunging, quick reflexes - so I built his matches around that," says Cash who worked closely with director Richard Loncraine in choreographing the tennis sequences.

Paul was born in north London and from the age of nine grew up in Hertfordshire.

His father, Thane, is an actor and his maternal grandmother, Olga Gwynne, was a successful stage actress. Paul studied at the Drama Centre in London and worked extensively in theatre, including a spell with the Royal Shakespeare Company, and on television (notably Lynda Le Plante's thriller Killer Net) in the UK before breaking into films with an outstanding performance as a psychotic London villain in Gangster No. 1.

Before his career took off he did several odd jobs to pay the rent - busking on London's underground and peeling potatoes in a fish and chip shop.

His other films include A Beautiful Mind, starring with Russell Crowe and his future wife, Jennifer Connelly, in Master and Commander, which re-united him with Crowe again, and Dogville with Nicole Kidman.

He lives with his wife and their one-year-old son Stellan and Paul's seven-year-old stepson Kai in London and New York.

In Wimbledon he plays journeyman Brit Peter Colt who has fallen from the giddy heights of being ranked No. 11 in the world down to a lowly 119. He has a wild card entry into the tournament which will be his swan song as a player. Nobody expects him to win, least of all Peter himself. But then he meets Lizzie Bradbury (Kirsten Dunst), a ferociously determined, enormously talented young American player and they fall in love. Lizzie's winning ways begin to rub off on Peter and the rank outsider progresses through the tournament. For Lizzie, though, her game starts to suffer - much to her father's annoyance. Played by Sam Neill Bradbury Snr tries his best to sabotage the relationship.

Q What did Cash teach you about the game?

A I spent a lot of time with Pat. A man called Steve Turner trained me in New York and Pat Cash would come in and oversee that and a man called Mike Hood took me through lifting really heavy things in the air a lot and then when we got to London Pat took over.

The most interesting thing was I was wondering what drove these people, you know I had to do it for ten months, six months of filming and four months of actual shooting, keeping fit and eating boiled chicken six times a day.

But these people do it forever. And I couldn't quite work out the drive because I don't feel that competitive and Pat said it was never about winning for him, it was about not losing. It wasn't so much about the elation of triumph more that he couldn't bear to be around himself when he lost, he hated that feeling so much. And I thought that was really interesting, that drive actually comes from a negative feeling rather than a positive - who wants to lose less, not who wants to win more.

Q Was it important that you had good chemistry' with Kirsten?

A I think chemistry is invented by producers and directors. To be honest, I think it's all about being relaxed. I mean, nobody ever said that me and Russell (Crowe) had good chemistry, it's always a man and a woman for some reason.

But the thing is when you work with someone like Russell, he's a very generous actor and it's relaxed and you can get great results in that kind of atmosphere. With Kirsten she's natural and very relaxed in front of the camera and that helps because then you can make happy mistakes.

Q How did it feel to develop an athlete's body?

A It's insane, I really feel for these American actors who have to keep buff the whole time, I mean it's really crazy. It's like poor Russell on this job at the moment (Cinderella Man), he plays a boxer and he's got himself down to 175lbs and it's like he said to me when you start hitting 40 that's work, that's hard work..' I found it enormously boring going to the gym. It's so funny the first gym I was taken to, their big marketing campaign was a huge poster that said think less and feel better..' I thought oh wonderful,that's the gym culture I'm getting into here..' and the truth of it is it's impossible to have an interesting thought when you're lifting a couple of hundred pounds of whatever Q Is it harder to make it look like you are playing well or badly?

A That's a really good point because the moment you do get into the choreography the temptation is when you can place the ball anywhere you choose because it's not actually there, you place it where you can hit it really sweetly. When in actual fact for this, it being kind of Rocky can he get to the ball?' and trying to lunge for something that isn't there, trying to struggle for something that isn't there, is much more difficult than placing it somewhere nice and easy for you.

Q You filmed some scenes before a full house on the Centre Court at Wimbledon in 2003. What was that like?

A It quickly goes from oh what an honour, to God this is nerve-wracking to oh my God this could be really humiliating..' It was the nearest to being a rock star that I'll ever feel. You go out and the crowd roar at you, it was amazing.