From his offices at Basinghall Street in the City of London, Henry Slater presided over Britain's best-known private detective agency, king of all he surveyed. In the late Victorian era, and into the twentieth century, his name was synonymous with the Golden Age of private detection; he was a truly modern operator, utilising the press and technology, and creating innovative publicity campaigns to keep his agency in the public eye.One of the key skills of the private detective was the ability to make friends - to infiltrate the lives of individuals, and to get them to trust them with their secrets. Slater, however, would make one mistake: to befriend the wrong person and to entrust them with his secrets. When that friendship ended, competition in the private detective world would lead to a trial so infamous that Winston Churchill himself came to watch proceedings play out at the Old Bailey. The trial would destroy Henry Slater's career, and expose his real identity.This is the first in-depth study of private detective work in nineteenth and early twentieth century Britain, looking at the 'Golden Age' of private detectives and the work they did. It provides a fascinating look at the type of person who became a private detective, the people who wanted to be their clients - and the crimes that could be committed along the way. This book sheds new light on this profession, building on the author's previous work on female private detectives in order to enable the reader to gain a better understanding of a job that people of all classes desired to do. But it is also about the career of one man. Sherlock Holmes may have been the most famous fictional private detective, but Henry Slater was, for twenty years, the real star of the private detective world.