Sherlock Holmes is the most famous fictional detective in the world. It is 127 years since he solved his first case – ‘A Study in Scarlet’ published in the Beeton’s Christmas Annual in 1887 – yet interest in the great detective has never been higher. But what was the inspiration behind the character, and what made him so popular? Sir Arthur Conan Doyle, his creator, modelled Holmes’s lightning powers of observation and deductive reasoning on a real surgeon, Dr Joseph Bell, and added his own knowledge of fledgling forensic techniques, imbuing Sherlock with an unprecedented ability to solve crime in a completely revolutionary way. In doing so, he also changed the real world of police detection and deduction. The success of modern crime-solving owes much to Sherlock Holmes. Forensic scientists, crime historians and Sherlockian experts reveal for the first time how the fictional detective became a catalyst in the evolution of modern investigation, identification and the forensic sciences. Holmes was the world’s first individual to apply scientific methods to crime solving. He subjected each crime scene to an acute examination and used chemistry, bloodstains and minute traces of evidence to catch his man. In an era when eyewitness reports and ‘smoking gun’ evidence were needed to convict criminals, and police incompetence allowed Jack the Ripper to stalk the streets freely, Sherlock’s methods were revolutionary. He truly was the world’s first crime scene investigator.