“I suffer very badly from stage fright,” she says.
“I didn’t find it out until I had actually been on stage that that’s what the feeling was.
“It’s literally like having a wall in front of you. You know you have the ability to break through but for some reason you can’t on that day.
“It’s very strange that you can work as much as I do and still have a problem with that.”
She has found a way to circumvent her fears, a method that came in handy while making her newest film A Dangerous Method, the story of the fathers of psychoanalysis, Carl Jung (played by Michael Fassbender) and Sigmund Freud (played by Viggo Mortensen), and Sabina Spielrein, the intelligent but troubled patient who causes a falling out between the men.
“I found only in the last few years that research helps,” she says.
“As far as getting over that fear of stage fright I find that preparation is the key.”
To play Spielrein, a woman wracked by tics and repression, Knightley threw herself into the exploration of the character.
“There was nothing that linked me to her,” she says.
“I had no idea about it. So I phoned Christopher Hampton because he did the adaptation of Atonement, which I did a few years ago, and said, ‘I’m going to do this, so help. Just help.’
“I went round to his house and thought he was going to give me a talk for a couple of hours and give me all the answers but he just handed me a pile of books and said, ‘Start reading. It’s all in there.’”
She eased her nerves with the research and further support was supplied during shooting by the film’s director, David Cronenberg.
“Sets… are very difficult creative spaces,” she says, “and trying to get the space so you can use your imagination and get yourself so you are not frightened by however many hundreds of people are on the set is quite a difficult thing.
“What David does is entirely creative. As much as it is technical it is also creative, collaborative and everybody is incredibly respectful of each other.
“He’s a magician. He’s absolutely extraordinary.”
Viggo Mortensen on research
“With David (Cronenberg) I know I’m going to have a good time shooting and the movie is probably going to be really interesting and original. As is the case this time again. A lot of cases with other directors the shoot is maybe fraught with tension and disorder but the research period can always be interesting. I love that.”