Even so, the BBC series Sherlock, in particular, has stoked the most passionate strand of Holmes fandom in some time. The only difference is that now we’re used to super-fandom. Holmes fans have only grown more obsessive since then. He’d meant to make some money to support his real art, novels full of what he felt were important ideas and political statements. But he hadn’t meant to spend the rest of his life inventing and solving fictional crimes. The Strand would pay Conan Doyle nicely for whatever he could give them.

The demand for Holmes stories seemed endless. Historian David Payne describes them as “largely the lower-middle and middle-middle classes of the cities, the non-intellectual, non-public school, hardworking, rising… people – the first true mass moderns.” The Strand targeted them with what we’d now recognise as exciting, high-concept genre stories – mysteries and science fiction – from writers such as HG Wells and Jules Verne. They were the ones priced out of concerts, the ones who had to wait for the cheaper versions of popular novels. Holmes fans were truly the emerging middle-class, the exact sort of group whose tastes would be denigrated by snooty critics as populist for more than a century to come. Interestingly enough, Holmes’ intense following continues to this day, spawning endless reimaginings, such as the US crime-solving series Elementary and the BBC’s Sherlock, which returned with a highly-anticipated special on New Year’s Day, its modern-day Sherlock and Watson returning to Victorian times. Sherlock Holmes’ avid readers helped to create the very modern practice of fandom. They seemed to actually expect a reciprocal relationship with the works they loved. Now they were beginning to take their popular culture personally, and to expect their favourite works to conform to certain expectations. The term, short for “fanatic”, had only recently begun use in reference to American baseball enthusiasts.) Readers typically accepted what went on in their favourite books, then moved on. (In fact, they weren’t even called “fans” yet. But at the time, Conan Doyle had every reason to be shocked by the torrent of vitriol. This sounds, of course, like just another day on the internet in 2015. Conan Doyle stuck to his guns in the face of the protests, calling the death “justifiable homicide” – referring, presumably, to his own justifications, not Moriarty’s. Americans started “Let’s Keep Holmes Alive” clubs. (Some Holmes aficionados have suggested the story could have been an exaggeration perpetuated by Conan Doyle’s son in interviews.) Outraged readers wrote to the magazine in protest: “You brute!” one letter addressed to Conan Doyle began. Legend has it that young men throughout London wore black mourning crêpes on their hats or around their arms for the month of Holmes’ death, though that has recently been questioned.

The adventure of the empty house