From DR. BOLI’S ENCYCLOPEDIA OF MISINFORMATION.

Holmes, Sherlock. Sherlock Holmes was a real historical figure, although Dr. Watson embellished the character somewhat for publication. In particular, the cocaine addiction of the stories was in reality no more than a mild dependence on caffeine to get him going in the morning. The iconic deerstalker was also an invention of Watson’s, the real Holmes preferring a tractor cap. The character of “Arthur Conan Doyle” is, of course, entirely fictional.