By the end of the nineteenth century, reform and development of the British electoral system had inaugurated a new style of mass politics which fundamentally transformed the face of the British party system. This book traces the evolution of recognisably modern parties from their roots in the 1880s through half a century of dramatic change in organisational structure, electoral competition and constitutional thought. In the House of Commons the Labour Party replaced the Liberals as the radical answer to the Conservative Party. In the country at large the complex web of Victorian social, regional and religious allegiances gave way to a cruder but more dynamic model of modern political loyalties. The transformation at Westminster and in the constituencies is surveyed in relation to changes to the franchise (including the vote for women), class consciousness, political organisation and doctrine. The comprehensive account explains the varying fortunes of the parties in the face of mass democracy, collectivism, the First World War and economic uncertainty. It also provides a critical insight into the debates and conflicts of interpretation which surround this pivotal period in British political history.