The plot thickens

However, one of the books in the new batch of Holmes books is particularly interesting. First published in 1979, Prisoner of the Devil by Michael Hardwick and Simon Haugh has been revised for a new edition, to be published early in the new year, and has the distinction of being the only Holmes spin-off or pastiche endorsed by Dame Jean Conan Doyle, the daughter of Sir Arthur. “This book has caught my father’s style marvelously,” she said.

The Prisoner of the Devil also achieved the near impossible and broke new ground by placing Holmes at the centre of a true story, in this case the trial and wrongful imprisonment of Alfred Dreyfus, the French artillery officer who was famously convicted of treason and imprisoned on Devil’s Island in French Guiana. The case, in which Dreyfus was accused of passing information to Germany, was a cause celebre in the 19th century and Sir Arthur Conan Doyle took a keen interest, so it is entirely appropriate for it to be at the heart of a Holmes case.

In the novel, Holmes and Watson are approached by Alfred Dreyfus’s brother Mathieu, who is desperate to prove that his brother is innocent. In reality, it was a man called Georges Picquart, the head of French military intelligence, who uncovered evidence pointing to another officer as the traitor, but in the novel it is Holmes’s dogged, logical detection that reveals the truth. And the case is even more interesting because the fictional version of the story exposes one of the real reasons that Dreyfus was accused: anti-Semitism (at a time when it was rare, Dreyfus was a Jew working at the height of French society).

The plot of Prisoner of the Devil and the idea of Holmes’ involvement with Dreyfus was developed by Simon Haugh and the late Michael Hardwick. Hardwick was a committed fan of Holmes; Haugh on the other hand did not move in Sherlockian circles but was enthusiastic about the idea of putting the detective in the middle of the Dreyfus case.

Speaking from his home in London, Haugh says he and Hardwick were also writing at a time when Holmes spin-offs were not very common. “This was a time when Holmes books weren’t knocked out the way they are these days,” says Haugh. “It was also at a time when Holmes was still in copyright but our editor Mike Brecher knew who owned the copyright and he was able to do a deal.”

The resulting novel does manage to capture the tone of Holmes and Watson and that particular way Watson speaks: slightly credulous, slightly breathless, slightly pompous.

“There’s something about the language in which the originals and the best of the pastiches have been written and I’d like to think that Michael, with a little help from me, wrote pretty much the most faithful reproduction of the style, the tone, the voice of the originals,” says Haugh.

“Certainly, Dame Jean believed that. It wasn’t that Dame Jean had the idea that she could make money out of licensing the rights, but she was a zealous guardian of her father’s literary heritage. She had lost control of any rights, so when Michael, who knew her, sent her a copy of the books, she did not have to say anything about it, but she did very enthusiastically endorse it so I think she also probably believed that this was one of the best Holmes books not written by her dad.”

Quite what Dame Joan, or indeed Sir Arthur, would make of the Holmes novels that have appeared since is hard to say, although their understanding of what the Holmes stories are would certainly be stretched. Some of the first non-canonical Holmes stories were written by Sir Arthur’s son Adrian in collaboration with the great crime novelist John Dickson Carr in the 1950s and they stuck fairly closely to the original conception. However, many of the stories and novels published since then have pushed the boundaries and taken Holmes into some unexpected territory.

The 1974 novel and film The Seven-Per Cent Solution, for example, follows Holmes as he attempts to conquer his cocaine addiction with the help of Sigmund Freud, but there have been even more unusual takes. Robert Lee Hall’s Exit Sherlock Holmes for example has the voice of Watson down pat, but it has the most extraordinary twist that takes the book into an entirely new genre. Holmes also fought Dracula and Dr Jekyll in short stories by Loren D Estleman and W Wellman’s Sherlock Holmes’ War of the Worlds has the detective and his sidekick fighting the aliens from HG Well’s famous novel.

More recent evocations have been more faithful. In 1995, the American novelist Caleb Carr produced The Italian Secretary, in which Holmes investigates a murder in the wing of Holyrood Palace where Mary Queen of Scots’ lover David Rizzio was killed. More recently, Anthony Horowitz has produced two novels: The House of Silk and Moriarty, which is set immediately after the incident at the Reichenbach Falls.

Simon Haugh is slightly bewildered by all of these books and the sheer number of new Holmes works, but thinks the reason there are so many might be because, beyond Holmes, Watson, 221b, and the odd appearance of Mrs Hudson the housekeeper, Mycroft and the Baker Street Irregulars, there aren’t many rules to follow.

“I can’t think of another character that has inspired so many follow-ups,” he says. “Nowadays there’s the TV series which is not in period so it now seems as if anything goes. Back in the day when we were working on the book, I would have said, providing it’s in period, you can put him almost anywhere. He has appeal to successive generations and there are few other Victorian characters that have become quite so enduring.”

Art in the Blood is published by HarperCollins at £12.99. The Adventure of the Ruby Elephants is published by MX at £8.99. Mycroft Holmes is published by Titan at £17.99. Prisoner of the Devil is published by Mean Time on February 25 at £8.95.