Keira Knightley's newest film involved a lot of complex mathematics, but did the British actress understand any of it?

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Knightley stars as code breaker Joan Clarke in The Imitation Game with Benedict Cumberbatch and revealed to The Daily Mail that she was "really bad at it."

"I was really bad, really bad at all of it and I didn't understand any of the maths," the actress admitted. "We had a specialist brought in and I got that feeling that I haven't had since school doing maths. You sort of feel like you've died and I couldn't concentrate at all. But he was such a nice man and it's really interesting and I should have been paying attention but I didn't!"

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Knightley even revealed that the cast tried to do a crossword puzzle and it ended up taking them five days to complete, so its no surprise her skills didn't improve.

Knightley wowed during the London premiere for the film in an ankle-length flowered dress at the opening of the BFI Film Festival with costar Cumberbatch.

Cumberbatch may have understood a little more than Knightley, but not that much. "I did understand a bit, a bit about the enigma machine and the coding but put an algorithm in front of me now," he joked, "or a quadratic equation and this press conference would never end for me trying to work it out."

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