Awards now also seem likely for The Imitation Game, which won the audience award at the Toronto Film Festival, as 12 Years a Slave and The King's Speech had done in previous years but no manner of research was ever going to make mathematicians of the actors.
"I spent two weeks desperately trying to understand what they were talking about and desperately trying to get my head around some of the theorems," Knightley recalls. "But I felt like I didn't understand a thing."
In the film, an awkward Clarke gingerly arrives late for the crossword puzzle test that Turing has determined will separate the men from the boys, only to discover that a woman does it faster than anyone.
Unsurprisingly, the actors were hopeless at crossword puzzles, too. "We all tried getting them to work and it took us two days to do half of one quick crossword," Knightley recalls. "So it's definitely not my forte."
How does she deal with today's technology, given that that Turing's machine was essentially the first computer?
"I hate it."
She doesn't use Twitter or Facebook?
"No, not interested," she replies curtly, noting that her husband, Klaxons' frontman James Righton does. "They have to do it. It's part of their business."
Knightley had been in relationships with the actors Jamie Dornan (The Fall, Fifty Shades of Grey) and Friend (now on Homeland) before she met Righton, whom she married in May last year in the hilltop village of Mazan in the south of France.
"Marriage is great. I highly recommend it," she beams but admits "it's easier being with someone in the creative industry".
"You spend most of your time away. It's a very specific lifestyle. It's very difficult to have a relationship with someone who's in one place living nine to five who cannot get to where you are or you cannot get back to. I think an understanding of that lifestyle is the reason you end up with people who are cool with that."
How does it work? "You try and mark out the time that you're working and then you spend a lot of money on plane tickets and you get very tired. James comes to the set whenever he can."
An advantage with The Imitation Game was that it was filmed in England, including at Bletchley Park, an hour and a half outside of London. Knightley still lives in London where she was born and raised as the only daughter of actress-turned-playwright Sharman Macdonald and actor Will Knightley.
"My parents weren't alive during the war but my grandparents were. There's this story of my Nan falling down the stairs with my uncle in her arms because a bomb hit right next to the house.
"I remember as a kid being at friends' houses and there were still bomb shelters in the gardens where we used to play. I remember walking around London asking, 'Why is that building new when the next one's old?' You can't be a Londoner and not walk around with the scars of the war a little bit."
Knightley recently spent six days portraying a pregnant Jan Arnold, the wife of New Zealander Rob Hall, in Everest, about the 1996 expedition that went horribly wrong.
"It was wonderful to meet Jan. She's amazing," Knightley says. "My scenes were about the conversation she had with her husband on the day he died on the mountain.
"Jan was on the set to see the filming and listening to the recording of her last conversation with her husband also helped me. I'm in the film for, like, five seconds but it's such a fascinating story and from what I've seen it looks great."
The Australian actor Jason Clarke plays Hall. "God, he's a f***ing good actor. The couple of scenes I did with him were pretty special. Jake Gyllenhaal's also in it - it's a wonderful cast. But I didn't see anybody apart from Jason."
Probably just as well because it's all blokes again.
"Like most films, you know
The Imitation Game opens New Year's Day.
