Green Silk Satin Maxi Dress: Open Back Wedding, 'Atonement' Style Anyone else still thinking about Keira Knightley's backless green dress from Atonement, 13 years later? At the link in bio, our style editor examines why the backless trend became an unlikely Kiera Knightley's iconic emerald gown from 'Atonement' remains one of cinema's best fashion moments. Here, see where it ranks on our roundup of the most stunning period costumes ever seen on film: Keira Knightley shines in emerald gown at Harper's Bazaar awards Irish Mirror