After pictures emerged of the Sherlock actor with a brunette companion at the French Open, the 38-year-old's legion of fans sought to identify his new love interest.
Benedict and Sophie attended the French Open in June together
On Saturday The Mirror confirmed that "for a number of weeks" Benedict has been seeing 36-year-old Sophie, an Oxford graduate who appeared in 2004 blockbuster Vanity Fair as well as TV shows including Midsomer Murders and Torchwood.
Benedict and Sophie have known each other for some time and starred together in 2009 film Burlesque Fairytales.
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When quizzed about her daughter's relationship with the 12 Years A Slave actor, Sophie's Edinburgh-based mum Anna cryptically told The Mirror: "Watch this space. You never know."
Sophie, who played Anne Boleyn in Henry VIII: Mind of a Tyrant, studied French and Italian at Oxford before undertaking a course at the Jacques Lecoq school of theatre in Paris.
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Harrow-educated Benedict, who studied drama at Manchester University, has previously been romantically linked to designer Anna James and dated The Thick of It star Olivia Poulet for 12 years.