English radicalism has been a deep-rooted but minority tradition in the political culture since at least the seventeenth century. The central aim of this book is to examine, in historical and political context, a range of key events and individuals that exemplify English radicalism in the twentieth century. This analysis is preceded by defining precisely what has constituted this tradition; and by the main outline of the development of the tradition from the Civil War to the end of the nineteenth century. Three of the main currents of English radicalism in the twentieth century have been the labour movement, the women’s movement and the peace movement. These are discussed in some detail, as a framework for the detailed consideration of ten key representative figures of the tradition in the twentieth century: Bertrand Russell, Sylvia Pankhurst, Ellen Wilkinson, George Orwell, E.P. Thompson, Michael Foot, Joan Maynard, Stuart Hall, Tony Benn and Nicolas Walter. The question of ‘agency’ – of how to bring about radical change in a predominantly conservative society and culture – has been a fundamental issue for English radicals. It is argued that, in the twentieth century, many of the important achievements in progressive politics have taken place in and through extra-parliamentary movements, as well as through formal political parties and organisations – the Labour Party and other socialist organisations – and on occasion, through libertarian and anarchist politics. The final chapter considers the continuing relevance of this political tradition in the early twenty-first century, and reviews its challenges and prospects.