Keira Knightley's edginess while playing a real-life Iraq War whistle-blower in the political thriller "Official Secrets" wasn't all an act. The decision to sleep train her 3-year-old daughter during filming meant she wasn't faking it when it came to the emotional side of the role.
"I felt very on edge, but for different reasons. So I used it all," Knightley joked during a recent interview.
It's not a method she'd recommend to her fellow thespians.
"Any actresses out there, do not move the child from the cot to the bed when you're just about to play a lead role in a film that has a lot of words in it because remembering them is quite tricky," Knightley said.
The actress had a lot of important lines playing Katharine Gun, a translator at the British government's communications headquarters in the early 2000s. While there, Gun leaked a confidential United States National Security Agency email exposing illegal activities to a British newspaper.
The memo proved that the U.K. and U.S. governments were in collusion over spying on countries that were wavering in their support for the war. After the information hit the front pages of newspapers, Gun confessed and was subsequently arrested and charged under the Official Secrets Act.
Knightley admits that despite being a politically engaged 18-year-old at the time of the Iraq War, she had no memory of Gun's extraordinary story.
"I was sort of fascinated that either I'd forgotten, or I'd never known about Katharine Gun and I'd never known about this memo. So I felt like, you know, just as far as kind of a historical piece in sort of shedding light on that, the lead up to that conflict, I thought it was a very important story to tell."
The film traces Gun's arrest and landmark criminal trial and Knightley said she was most concerned with accurately depicting Gun's actions.
"When you meet Katharine, her point of view is absolutely clear and you know my job in this was telling this story from her point of view completely," Knightley said.
This was an immense challenge: Gun still can't speak freely about what happened.
"It was the first time I've ever met somebody, and I was asking questions and I thought, 'Oh they actually legally cannot answer the question,' because of course she is still bound by the Official Secrets Act. So I can't say that you know I got anything that isn't in the public domain but she is a fascinating, extraordinary woman."
The film's supporting cast includes Matt Smith as newspaper journalist Martin Bright, Matthew Goode as fellow journalist Peter Beaumont and Ralph Fiennes as defense lawyer Ben Emmerson. "Official Secrets" opens in the United States on Aug. 30 and in the U.K. in October.