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 by critic Rachel Read as being “delightful”.

In 2008, Riley began dating billionaire entrepreneur Elon Musk and in 2010 they married at Dornoch Cathedral. In January 2012, Musk announced that he had ended his four-year relationship with Riley, and sought a divorce by March 2012.

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 also played Mary Bennet in the 2005 version of Pride and Prejudice, acted in the role of Marianne in 2009’s The Boat That Rocked, and starred in the 2007 film St Trinian’s and its 2009 sequel St Trinian’s: The Legend of Fritton’s Gold. She also appeared in White Frog.

She was featured on the March 2010 cover of Esquire.

In 2011, she was named a “Brit to Watch” by the British Academy of Film and Television Arts.

In July 2013, however, Musk and Riley remarried. In a 60 Minutes interview in 2014, the couple stated that they had reconciled and were living together again, along with Musk’s five children from his first marriage to writer Justine Musk.

On 31 December 2014, the Associated Press reported that Musk had filed for divorce; however, the action was withdrawn. It was reported that Riley had been living separately from Musk for six months and filed for a second divorce in Los Angeles Superior Court on 21 March 2016. The divorce was finalised in October 2016.

Her debut novel, Acts of Love, was published by Hodder & Stoughton in August 2016.