Keira Knightley, Cecilia Tallis - Atonement Costume Design by Jacqueline Durran The dress, which is precisely the way it was described in the novel, deserved an Oscar for bewitching beauty. The film? The book otoh is fascinating.
This modern imitation of the Flapper dress is from Marchesa's Fall 2015 RTW Collection. The fringes on the bottom are what the flapper dresses in the were like. This designer modernized the look by adding puffy sleeves.