By Keily Oakes BBC News Online entertainment staff

In romantic comedy Wimbledon, the unlikely hero is a polite British tennis player on the wrong side of the hill who is pitted against an aggressive US whizzkid.

While the pomp and circumstance of the Wimbledon Tennis Championships is an integral part of the film, it is balanced by a love story between two players.

Wimbledon sees Paul Bettany take his first romantic lead

Paul Bettany plays the British player who has no confidence in his game and is all set to retire and take up a cushy job teaching tennis to excitable ladies.

But this could well be his year for not only winning a trophy but also the girl of his dreams, the feisty American player Lizzie Bradbury, played by Kirsten Dunst.

Wimbledon sees Bettany step out of the shadows of Russell Crowe, who he has played sidekick to twice, to much acclaim, in Master and Commander and A Beautiful Mind.

It is also his first shot at romantic comedy lead, and with actress-of-the-moment Dunst next to him the expectations are high.

Bettany's performance will inevitably draw comparisons with Hugh Grant because Wimbledon is a Working Title film, the production company behind Notting Hill, Bridget Jones and Love Actually - all vehicles for Grant's bumbling but loveable style.

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Bettany was keen to distance himself from Grant's distinctive delivery.

"I think initially the film was developed with Hugh in mind and then he got too old," joked Bettany.

"We did consciously steer away from doing what he does very elegantly, and frankly because he has a quality that I think Cary Grant and Will Smith have, which is a sort of relentless charm that doesn't get dreary.

"I do enjoy watching him and I thought 'you're never going to be able to do that', so I tried to do something different."

The film is directed by Richard Loncraine, himself a newcomer to the rom-com genre, having directed the Emmy-winning dramas The Gathering Storm and My House in Umbria.

He was surprised at how difficult it was to shoot a romance.

Paul Bettany plays British player Peter Cole

"It was much harder than you think and that was the thing that shocked me. I think all directors are arrogant, so I thought it would be quite easy to do one," said Loncraine.

"The fact that it's not just a romantic comedy but a film with sport in made it twice as difficult, so we were constantly trying to balance one against the other. It was pretty tricky."

One of the biggest challenges of the production was persuading the All England Lawn Tennis Club to allow an entire film crew on to the hallowed turf, something they are very precious about.

"They were very nervous about us making a film there because Wimbledon is a very valuable property in their eyes and a lot of damage could have been done," said Loncraine.

"Once they had accepted us, they were fantastic."

Filming eventually began at the 2003 championships, using real crowds.

John McEnroe and Chris Evert play themselves in the film

Loncraine admits some literary licence was used in filming the tennis games, particularly because the base line game employed by today's top players could have made for dull viewing.

Ex-Wimbledon champ Pat Cash was drafted in to act as technical advisor, teaching Bettany and Dunst how to look like real pros.

He also choreographed the moves between the actors, with CGI tennis balls inserted later on for many of the shots, which led to Bettany pretending to play a proper match in front of a capacity crowd without a ball.

And it was not only the balls that were fake.

McEnroe's role

In the final game 7,500 blow-up dolls were put into the crowd to fill it out because the real tournament had ended by that stage, and it would have proved too costly to use real extras.

Another former Wimbledon winner, John McEnroe, was hired to play a commentator, alongside Chris Evert.

But Loncraine said he wanted to avoid using real tennis players in the games, admitting he turned down the opportunity to use reigning women's champ Maria Sharapova, who at the time the production began was still relatively unknown.

He said the reason he turned her down was that, as a blonde, it would have been too difficult to tell her and Dunst apart in long shots.

Feeling furious

Bettany admits his PE teacher from his days growing up in Harlesden, north-west London, would be surprised to see him portraying an athlete on film.

"I think they would be entirely shocked by the whole idea of my being in a film like this because I'm not just not driven like that.

"I did play football at school, but if I'm really honest I never really cared if the other school won or lost. I never felt that kind of commitment to something - or anything other than myself," he joked.

Although taught by one of the masters of the game, Bettany said that after he smashed his tennis racquet at the end of filming he vowed not to pick it up for a while.

"I loved playing and learning to play, but as the start date for the movie got nearer I stopped enjoying my mistakes and ended going home feeling furious - and I wanted to be able play for fun again and enjoy it."