Classified lifts the lid on the hidden world of sex, violence, perversity and mystery that lay behind the personal ad in twentieth century Britain. Like the internet today, the personal ad was the centre of many different fears and anxieties. From the 1890s onwards, a hidden world of sex lurked behind ads for “companions,” and lonely soldiers, special “chums” and matrimonial proposals. Some led to friendship, love and even marriage, while others led to terrible crimes, even to murder. Classified tells us some of these stories. It tells us how ordinary people (and British society as a whole) tried to think their way through sexual liberation, homosexuality, pornography, modern marriage, the gifts and trials of single life, and all of their attendant perils and opportunities, long before these became the everyday preoccupations of the present. For much of the twentieth century, the personal ad was a symbol of everything that was both exciting and scary about modern sexuality.