And when the curtain went up on Wednesday (09Feb11), the Pirates of the Caribbean star managed to impress the audience and draw praise for her role as a headmistress accused of having a lesbian affair with her colleague.
Charles Spencer of Britain's Daily Telegraph wrote that Keira Knightley "displays confidence throughout before rising in the final act to dramatic heights that are shattering in their intensity."
The Guardian's theatre critic Michael Billington said Keira Knightley and her co-star Elisabeth Moss "prove as potent a combination on stage as at the box office", adding: "(The) atmospheric, slow-burning and ultimately enthralling production proves far more compelling than I expected."
Meanwhile, filmmaker Gurinder Chadha, who made Keira Knightley a film star after casting her in Bend It Like Beckham, was blown away by the actress' performance.
She tells the Press Association, "I thought it was very powerful, I'm a bit overcome. I'm so proud of Keira."