Brenda Blethyn, Vanessa Redgrave and Romola Garai have joined the cast of helmer Joe Wright’s “Atonement,” which started shooting in the U.K. last week.Pic stars Keira Knightley and James McAvoy, with a script by Christopher Hampton adapted from Ian McEwan’s novel. Newcomer Saoirse Ronan will play a 13-year-old who damages the lives of all around her when she accuses her sister’s boyfriend of a crime he did not commit. The movie is produced by Tim Bevan, Eric Fellner and Paul Webster for Working Title. Exec producers are Richard Eyre, Robert Fox, Debra Heyward and Liza Chasin. Focus Features will handle distribution in North America, with Universal Pictures Intl. releasing the movie in the rest of the world.