Taking inspiration from a police informer’s comment that his workmates had gone “Spain mad” in response to the Spanish Civil War, this book uses biographical studies to explore the nature of British engagement with the conflict. The opening chapter presents a general analysis of the subject and assesses the available evidence. Some 2400 Britons volunteered to fight in the conflict and some 500 died there. Accordingly, the International Brigades are well represented in the book, with chapters on two of the commanders of the British Battalion (Wilfred Macartney and Fred Copeman) and the Anglo-Canadian volunteer Frank Whitfield. Two of the other subjects (George Orwell and Felicia Browne) fought in other units. However, the book shows that engagement in the Civil War could take many forms: hence, the chapters on the journalist Philip Jordan, clergyman E.O. Iredell, and the humanitarian activist and politician G.T. Garratt. The remaining chapters look at three historians and writers who have shaped the understanding of the Civil War in Britain: Orwell, Hugh Thomas and Jim Fyrth. The book is based on extensive new research, and many of these subjects have never previously been studied in any depth.