Keira Knightley finds what is, for me, her defining role in director Joe Wright’s elegant, stirring and well-judged adaptation of Ian McEwan’s Booker-shortlisted novel about upper-class life between the wars. Although the story, brilliantly adapted by Christopher Hampton, is told through Briony Tallis (played by Saoirse Ronan as a girl, Romola Garai as a young woman and Vanessa Redgrave as her older self – quite a trio!), it is the impact of a certain, life-changing indiscretion upon upstairs-downstairs lovers Cecilia (Knightley) and Robbie (James McAvoy) that forms the meat of the film. What is essentially a story about writing is grandly fleshed out into a proper period epic, mixing country-house melodrama with Second World War adventure. Knightley brings an uncommon depth and poise to a part that might, 60 years ago, have rightly gone to Celia Johnson. Also, when the supporting cast features Benedict Cumberbatch, Daniel Mays and Brenda Blethyn, you know it’s something special.