Guy Ritchie’s true subject has always been London; the moneyed, brutish boxer’s fist that knuckles the Thames. London, that city of thieves, scoundrels and massively over-priced hotels, where the air turns your snot black and the weather drives a shiv into your bones. Like New York, but without the iconic silhouette, London is known more for its streets than its skyscrapers: Downing Street, Fleet Street; Carnaby Street. Even London’s most famous detective has a famous address: 221b Baker Street, home of Sherlock Holmes. In Guy Ritchie’s new movie, the cerebral sleuth returns to a city rank with wrongdoing. London’s tourists will know it well.