The book phenomenon of `Club Government' in the mid-nineteenth century, when many of the functions of government were alleged to have taken place behind closed doors, in the secretive clubs of London's St. James's district, has not been adequately historicized. Despite `Club Government' being referenced in most major political histories of the period, it is a topic which has never before enjoyed a full-length study. Making use of previously-sealed club archives, and adopting a broad range of analytical techniques, this work of political history, social history, sociology and quantitative approaches to history seeks to deepen our understanding of the distinctive and novel ways in which British political culture evolved in this period. The book concludes that historians have hugely underestimated the extent of club influence on `high politics' in Westminster, and though the reputation of clubs for intervening in elections was exaggerated, the culture and secrecy involved in gentleman's clubs had a huge impact on Britain and the British Empire.