This is the first in-depth study of the involvement of businessmen in the campaign for Tariff Reform, the most important and pervasive political debate on British economic policy in the first three decades of the twentieth century. This book is organized around an analysis of the pressure and propaganda groups directed, or supposedly directed, by protectionist businessmen themselves. The book includes the first in-depth investigation into the development of protectionism during the First World War, and presents a new analysis of the turbulent events of 1929-1932.