Keira Knightley was at the Venice Film Festival last night for the world premiere of Atonement.

She was joined outside the Palazzo del Cinema by co-star James McAvoy, who was there with actress wife Anne-Marie Duff.

Director Joe Wright was accompanied by girlfriend Rosamund Pike while Vanessa Redgrave made it a family affair by arriving with daughter, Joely Richardson.

Also enjoying her big moment - and her first premiere - was 13-year-old Saoirse Ronan, who plays Knightley's younger sister in the film.

Atonement was chosen as the curtain-raiser for the festival and is being hailed as one of the strongest British films in years.

Adapted from the novel by Ian McEwan, it is in contention for the Golden Lion award for best film.

It is one of several British films vying for the prize - the others are Sleuth, a remake of the 1972 whodunnit directed by Kenneth Branagh with Jude Law and Michael Caine in the title roles; It's A Free World, Ken Loach's study of migrant labour in the UK; and Nightwatching, Peter Greenaway's Rembrandt mystery starring Martin Freeman.

Knightley is already being talked of as an Oscar contender for her performance in Atonement.

The 22-year-old plays Cecilia Tallis, an upper class beauty whose fledgling love affair with the housekeeper's son (McAvoy) is destroyed by a tragic misunderstanding.

The romance is doomed by her sister, Briony (Ronan), a young girl with a vivid imagination. Redgrave plays Briony as an older woman.

All eyes were on Knightley earlier in the day when she attended a press conference to promote the film.

She said: "What this film shows is the danger when the line between fiction and fact gets blurred.

"Magazine pictures, for example, are fiction. One person has done the make-up and hair, it's somebody else's clothes, it's choreographed by someone else.

"In the media, it's very important to see different varieties of people - old, young, whatever size. As a woman myself, I want to see variety. Hopefully, that will happen more."

Atonement is directed by Joe Wright and is only his second film. His first, Pride and Prejudice, also starred Knightley.

One of the most impressive scenes in the movie is a recreation of the evacuation of Dunkirk, which was filmed on the beach at Redcar using 1,000 local men as extras.