Sienna Rose Diana Miller is an American-born British actress. Born in New York City and raised in London, she began her career as a photography model, appearing in the pages of Italian Vogue and for the 2003 Pirelli calendar. Her acting breakthrough came in the 2004 films Layer Cake and Alfie. She subsequently portrayed socialite Edie Sedgwick in Factory Girl (2006) and author Caitlin Macnamara in The Edge of Love (2008), and was nominated for the 2008 BAFTA Rising Star Award. Her role as The Baroness in G.I. Joe: The Rise of Cobra (2009) was followed by a brief sabbatical from the screen amid increased tabloid scrutiny.

Layer Cake is a 2004 British crime film directed by Matthew Vaughn, in his directorial debut. The screenplay was adapted by J. J. Connolly from his 2000 novel of the same name. The film was produced by Adam Bohling, David Reid and Vaughn, with Stephen Marks as executive producer. The title refers to the social strata, especially in the British criminal underworld. The film's plot revolves around a London-based criminal, played by Daniel Craig, who works in the cocaine trade and wishes to leave the drug business. The film also features Tom Hardy, Michael Gambon, Colm Meaney, and Sienna Miller. Craig's character is unnamed in the film and is listed in the credits as "XXXX".