Keira Knightley faces her toughest screen challenge to date as the tragic Anna Karenina. The newly engaged actress reveals her thoughts on love and how she had her male co-stars quaking in their boots.

She’s one of the most famous women in the world but it’s no secret Keira Knightley detests any form of inquiry into her private life.

It’s brilliantly demonstrated by the steely look that flashes across her doe-like eyes at the mention of her engagement to James Righton.

He’s the 29-year-old Klaxons keyboardist she met through mutual friend Alexa Chung, following failed long-term romances with model James Dornan and actor Rupert Friend. The reference may only be to congratulate her on her forthcoming nuptials but it’s enough for the 27-year-old to close imaginary shutters – with a bang.

But it’s only momentary.

Asked if she thinks she’s learned anything about love from starring in Leo Tolstoy’s sweeping romance, Anna Karenina and the famous pout breaks into a wide grin. “God no!” she says. “Far too bleak, no, better to ignore the whole thing I think.”

In Anna Karenina, Knightley plays the young wife who scandalises 19th century Russian society by abandoning her dull but powerful husband Karenin, played by a balding and bespectacled Jude Law, for the dashing Count Vronsky, depicted by Aaron Taylor-Johnson.

It marks her third collaboration with the filmmaker Joe Wright, the man who famously banned the actress from pouting on screen. In 2005 he directed her to an Oscar nomination as Elizabeth Bennet in Pride and Prejudice and two years later to a BAFTA nomination in the Second World War romance Atonement. In tackling the doomed protagonist, Knightley is showing the world that the tomboy who delighted audiences in Bend It Like Beckham a decade ago is now cementing her status as an accomplished and versatile actress.

And Anna Karenina is indeed one heck of a part, one that’s previously been played by such acting greats as Vivien Leigh and Greta Garbo. Knightley herself has referred to the role as the female equivalent of Hamlet.

“I remembered the book as being just incredibly romantic with this extraordinary character but in re-reading the novel I suddenly went, ‘Oh my God, this is dark’,” says Knightley. She recalls lengthy discussions with Wright and screenwriter Tom Stoppard about Anna’s complexities. Her fear of simplifying the multifaceted Anna meant she immersed herself in the character to a point that she couldn’t always shrug her off at the end of the day.

“She did definitely come home on a couple of occasions and I don’t think I was the easiest person to live with when I was playing her,” reveals Knightley.

“But that’s part of the experience of playing a character like that.”

Having said that, she doesn’t believe Anna to be the toughest role she’s undertaken.

“Someone like Elizabeth Bennet is more terrifying because it’s a character that people love,” says Knightley. “They fall in love with her and they see themselves as her. People don’t see themselves as Anna.

“They see her as this strange creature so, from that point of view, it’s not as terrifying. But there’s always a responsibility, particularly when it’s a story that’s been done so many times,” she says.

Daughter of actor Will Knightley and playwright Sharman McDonald, the Richmond-born actress says she found the dancing required of her in the vital ballroom scene, in her own words, “a nightmare”.

“I think I’m quite quick at picking things up like that but actually I did find this impossible,” she says, laughing. “I’m not a dancer so it was really tricky.”

She’s not a singer either but says “I gave it my best shot” in her next venture Can A Song Save Your Life? which she recently finished in New York.

“Anna Karenina was such an incredibly intense, wonderful experience but it’s so dark and the depths that Anna goes to were quite tiring,” says Knightley.

“So I went away to New York and did this incredibly positive film.”