The thesis uses the political career of Josiah C. Wedgwood to examine the changing nature and significance of British Radicalism from the Liberal election victory of 1906 to the fall of the first Labour Government in 1924. It considers the nature of pre-war Radicalism and shows how Wedgwood built on older Radical traditions to mould an ideology that was still influential in Liberal politics, particularly in relation to land taxes, the defence of personal liberties, and native rights in Africa. It looks at the fluctuating fortunes of the Radicals after 1910 and the steps Wedgwood took to try and enhance their influence in British politics, and what this says about the vitality of the pre-war Liberal party, particularly vis-à-vis the Labour party. The thesis then explores Radical reactions to the outbreak of war, and how these changed over the following years as debates about conscription, the make-up of the Government, and war aims, gradually shattered the Liberal party and led to the migration of many Radicals to Labour. Wedgwood was an early and prominent post-war convert, and a key question for the thesis is to consider what factors prompted his move, their significance for the future prospects of the Liberal party, and to what extent, if any, he and other converts had to reconsider their ideological views in order to fit into the Labour party. The thesis then considers what effect, in terms of policy and political strength, the new recruits had on Labour. In Wedgwood's case, this means studying his views on fiscal, foreign and imperial policy and his influence in the Parliamentary Labour party. It considers why this influence declined from 1922, and reviews his anti-climactic experience in MacDonald's first Cabinet and what this says about the nature of the 1924 Labour Government.