Riley's television credits include episodes of Poirot (2003), Marple (2006), and Doctor Who (2008's "Silence in the Library" and "Forest of the Dead"). She also played Lila, a lovestruck writer, in the short-lived E4 series Nearly Famous (2007). Riley made her stage debut in The Philadelphia Story at the Old Vic in 2005. Her performance in a 2006 revival of Tennessee Williams' Summer and Smoke was described as "delightful". Riley appeared as a disguise used by Tom Hardy's character in Inception (2010). Also in 2010, The Summer House was released, which starred Riley in the lead role. By the end of the first day of release, it was the number one film on iTunes worldwide and dominated that position for several days. She was also cast in the film White Frog. She was featured on the March 2010 cover of Esquire.