Anna Friel adopted a tough new fitness routine to prepare for the rigours of playing Forties society girl Holly Golightly in Breakfast At Tiffany's, she admitted at the end of a nerve-racked first night.

Body Confident: Anna Friel is seen naked in the show

The waif-like star has been going to the gym five or six times a week and eating every two hours as part of the preparations for playing the role made famous by Audrey Hepburn in the 1961 film.

And while she appears naked on stage in one scene, the efforts were targeted less at the nudity than at achieving the deportment of a bygone era of hats and cigarettes in long holders.

More: Breakfast at Tiffany's review

“The Forties age was not one of slouching and you have to learn all of that — the way to talk, the way you move,” the 33-year-old actress said at the opening night celebrations attended by Sir Ian McKellen, Patrick Stewart, Rupert Everett and Richard E Grant.

Friel added that she was a “huge fan” of Audrey Hepburn and loved the role.

“It feels special for me. I'm loving it. There's not that many brilliant roles for women so it's wonderful to have the opportunity to play Holly. She is a great female part,” Friel said.

“And I really want to do more stage. I think stage-acting is a way of achieving longevity. I just want to get better and better.”

She has previously appeared in an Almeida production of Lulu, and also in the Broadway premiere of the Patrick Marber play Closer.

She still has a home in Los Angeles and hopes to be able to split time between London and the States if she and partner, Harry Potter actor David Thewlis, can juggle their schedules with bringing up their daughter, Gracie.

Thewlis played down parallels with Audrey Hepburn on what he said was a “lovely” night. “The comparison is to Audrey Hepburn but ultimately it's not [the director] Blake Edwards' vision but that of Truman Capote,” he said.

Sir Ian McKellen, Patrick Stewart, Paul O'Grady, Jeffrey Archer and Sir David Frost attended the star-studded opening night of Breakfast At Tiffany's at London's Theatre Royal Haymarket.

More pictures: Breakfast At Tiffany's press night