Keira Knightley - Keira Knightley: Anna Karenina Is The Hardest Film Ever

Keira Knightley: Anna Karenina Is The Hardest Film Ever

Keira Knightley regards 'Anna Karenina' to be the ''hardest'' film she's ever done.

The 27-year-old actress plays the titular character, an aristocrat in late-19th-century high society Russia who has an affair with Count Vronsky (Aaron Johnson) in the film adaptation of a book by Leo Tolstoy, and she found it really tough to get the balance of her character right because of the author's ''genius'' and ''complex'' writing.

The brunette beauty - who stars alongside Jude Law and Matthew MacFadyen in the drama movie - said: ''It was amazing. It was definitely the hardest thing I've ever done. In a brilliant way, in a brilliant way.

''Obviously, Tolstoy was a genius and I think the reason that his books last so well - is because they are so complex and it's really looking at the best of humanity and the worst of humanity, often in one character. And trying to balance all those things in the one person was really hard. And, hopefully it's worked.''

Another of Keira's latest movies sees her star in 'Seeking a Friend for the End of the World' - which sees Dodge (Steve Carell) search for his high school sweetheart accompanied by Penny (Keira) when the pair learn the apocalypse is imminent - and she was attracted to the project because it is so ''unusual''.

Speaking to HitFix, Keira added: ''I just never read anything like it. It's such an unusual piece and, actually, it's really rare to get things that are quiet unique and to read things you've never read anything like.

''And I just also thought, 'It's about the end of the world, but it's really positive.' And actually when I got to the end of The Script I found it quite life affirming as opposed to really sad or tragic or anything like that.''