A new thrilling two-part drama, Restless is set to hit our screens over Christmas.

Don't mention Christmas day cooking to Hayley Atwell, it will remind her of last year's disaster when she was head chef for her family. 'I really got into gingerbread houses and my Christmas Day showpiece was a rather ambitious attempt at a two-foot high one,' recalls the 30-year-old. 'It collapsed before the big day so we ate a crumbling ruin. There were a few frustrated tears about that!'

It's been a busy year for the actress, who has filmed an episode of Charlie Brooker's returning Black Mirror, a series called Life Of Crime about the police force, and a biopic about Jimi Hendrix in which she plays his 'hell-raising girlfriend'. All are out next year. But we can see her sooner than that in period spy thriller Restless, an adaptation of the William Boyd novel of the same name.

She plays Eva Delectorskaya, a beautiful Russian emigrant to Britain who gets scouted for the Secret Service by spy boss Lucas Romer (played by Rufus Sewell) after she discovers her brother was killed by the German secret service. 'At the start of the story she's plucked from a very vulnerable situation of losing someone close to her and is offered the opportunity to have a different kind of life. It's new, exciting and scary,' Atwell says.

Eva soon becomes professionally and romantically involved with Lucas but, when a spy mission in the US goes horribly wrong, she has to go underground and on the run. The character fascinated Atwell immediately. 'She goes on a huge journey. As a spy she lives double, sometimes triple lives and the movie touches upon the personal sacrifices she has to make for her survival. 'She is restless, always on the move, watching her back and thinking before she speaks. She can't even trust the man she loves. She is essentially completely alone and has to bravely trust her own instincts.'

Boyd, who adapted the book for screen himself, had a hand in casting Atwell as his Eva after they met on the set of his other adaptation, the Bafta-winning Any Human Heart. 'I had spent time with William Boyd and his wife on set and perhaps out of that relationship he thought of me for Restless,'' Atwell explains. 'It did feel that I was his first choice for Eva but of course, it had to go through the producers and director who ultimately made that decision.'

Atwell, who says she's shied away from 'sexy siren' roles because of the direction they might steer her career into, is proud to play Eva, who she thinks is an incredibly strong woman. 'She is a fighter but deeply emotional so I had to retain her emotional core as she transforms herself from one identity to another. I loved that her beauty is secondary to her skill and ability,'' she says.

Restless is on BBC One on Thursday December 27 and Friday, December 28 at 9pm.