In this authoritative book, Richard Wyn Jones traces the development of the political thought of Plaid Cymru from its birth in the winter months of 1924-5 to the establishment of the National Assembly for Wales in the summer of 1999. With a penetrating study of the political beliefs of Plaid Cymru's most important leaders - Saunders Lewis, Gwynfor Evans, Dafydd Elis-Thomas and Dafydd Wigley - Wyn Jones charts the party's emergence from the political fringe to the threshold of a devolved Wales. The development of the party's constitutional and economic policies is given close attention, as well as its attitude towards the Welsh language; and from a vibrant discussion on the nature of nationalism and nationalist ideas, Plaid Cymru's intellectual development takes its place within a broader historical and international context. The result reveals Plaid Cymru in a new and sometimes controversial light.