Cumberbatch, Knightley due on red carpet as 'The Imitation Game' opens London Film Fest

Keira Knightley says it's exciting to be opening the London Film Festival with World War II code-breaking story "The Imitation Game."

The film stars Benedict Cumberbatch as computer pioneer Alan Turing, who helped win the war but was later prosecuted for homosexuality.

Knightley, who plays fellow code-breaker Joan Clarke, said Wednesday that "it's lovely to be the first" of the 248 features screened at the 12-day festival.

"The Imitation Game" won the audience award at the Toronto Film Festival, often a precursor to Oscar success.

Director Morten Tyldum said playing the London festival was "like coming home" for the movie, which was shot in the British capital and at the nearby Bletchley Park code center.

The festival opens Wednesday and closes Oct. 19 with the Brad Pitt war saga, "Fury."