With such varied films as Pride & Prejudice (which earned her an Oscar nom) and Pirates of the Caribbean (which earned huge boxoffice), Keira Knightley nonetheless is extremely passionate about her current project, The Imitation Game. “This is a story that speaks to everyone,” she says of the Morten Tyldum-directed film about mathematician Alan Turing and the World War II code breakers of Bletchley Park. “When you understand what Turing and others did and who they were, this truly crosses national boundaries.” Knightley just received Screen Actors Guild and Golden Globe supporting actress noms, putting her in major Oscar contention for her portrayal of real-life cryptanalyst Joan Clarke, a friend and confidant of Turing’s. The role marks a deliberate new direction for the actress.

Your performance in The Imitation Game seems quite different from a lot of your work of years and films past.

I went through a period of playing very dark and neurotic characters, which I really enjoyed. And that was a very conscious decision on my part because that’s what I was really interested in. But I was interested in other types of roles as well. This chapter started with Begin Again and, for me, it was all about playing people who were much more relaxed—people who had a positivity because I felt I’d done five years of work where that hadn’t been the kind of main thing with (my) characters. I was interested in finding and playing with those sorts of characters and definitely Joan Clarke was one of them.

And yet, the film depicts a very dark time in the history of Britain and the West, in general, as the Nazis seemed almost unbeatable.

Yes, I mean, particularly when you’re talking about a drama dealing with such a serious topic and, during the second World War, with so much at stake. For me, to create a character with that positivity and that joy to her was a really interesting challenge, and something that I really enjoyed doing.

Was there an added sense of responsibly as an actor because of the subject matter, both the code-breaking work at Bletchley Park and the deep relationship between Alan Turing and Joan?

Of course. I was trying to do my job as well as possible. I mean, you feel that on every film, but this one—with Turing and Bletchley Park—everybody felt it was just such an important story to tell, so I think that’s definitely the case. You know, we only had eight weeks to film so you really had to come in being completely prepared and ready to go because you didn’t have the time to make any mistakes. And here, it was a group of very, very professional actors, so everybody was ready for that.

 To that end, how do you get prepared for a real-life character such as Joan?

I work a lot in historical dramas and one of the many reasons why I like working in them is because of the research. I just find all of that fascinating. It’s a good place to start for me. You know, you can find tiny little clues and little ideas that you can use all the way through.

 Was there a particular quality about her that you centered on?

She’s somebody who is so overtly trying to break that kind of glass ceiling. I was interested in the way she did it and the fact that she didn’t do it by trying to smash it. She didn’t do it by screaming and shouting, she did it by being a little bit like sunshine and being the person that people wanted to be with. I liked that funny quality of hers, that slightly airy quality.

 And she was so good with riddles and tests, as that wonderful crossword exam scene displayed. Honored as a Member of the British Empire, Clarke went on to have long and distinguished career at the U.K.’s GCHQ.

Yes, I was really interested in a character who is known for her intelligence. Yet, you know, when you think of a very intelligent character you sometimes think of them being quite hard and straight and sharp, and I wanted Joan to almost be the opposite of that. So I was definitely playing with those ideas, and again, I got that really from reading about her and from watching the documentaries where she’s featured.

While many of us know about the work done at Bletchley Park, the scope of Turing’s contribution and the terrible fate he suffered for his homosexuality remained hidden in many ways—especially here in America. As a Brit, did you know a lot about Turing?

I didn’t know about him until 2009, when there was this big push to get him pardoned. I think my sense of outrage of not having known about him, and anger about what had been done to him, is something that we definitely wanted people to feel when they saw this film. And I think that they have, and that’s fantastic.

You seem very proud.

I think just being a very, very small part in trying to get his name to a wider public, and his legacy to a wider public, is something very important to do. Yes, I’m very proud to have been a part of that.

 Keira Knightley photographed by Mark Mann