Alexa Chung Just Re Created Keira Knightley's Iconic Atonement Dress Who What Wear One Iconic Look: Keira Knightley's Green Gown in "Atonement" (2007) Tom + Lorenzo Atonement dress, Keira Knightley, Green Dress UK Velvet Birdcage Atonement dress, Keira Knightley, Green Dress UK Velvet Birdcage 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 She walked into the room, and time held its breath. Keira Knightley's emerald silk in Atonement (2007) wasn't just a costumeit was cinematic seduction. Named the best movie dress of all