Writing a new Sherlock Holmes story was daunting – but mine does something that hasn’t been done before | Gareth Rubin

The thriller writer on the responsibility, challenges and joy of writing an authorised new adventure

Smog-filled Victorian alleyways where villains lurk with glittering knives. Bleak heaths where giant devil dogs await the weary traveller. Blackmailers laughing at wide-eyed victims. All these have been my companions for half a year as I have felt my way through the landscapes of the world's most famous detective: Sherlock Holmes. Because a few weeks ago, authorised to do so by the Conan Doyle estate, and in a haze of 4am self-doubt, I finished writing a new official Holmes novel, Holmes and Moriarty.

In recent years, only one other author, Anthony Horowitz, has been allowed to write a new authorised novel; so it's been a riveting project - but a daunting one too.