The Bigods were one of the most powerful and important families in thirteenth-century England. They are chiefly remembered for their dramatic interventions in high politics. Roger III Bigod (c. 1209-70) famously led the march on Westminster Hall in 1258 against Henry III, while Roger IV Bigod (1245-1306) confronted Edward I in 1297 in similar fashion. This book is the first full-scale study of these two earls, and explores in depth the reasons that led each of them to take the extreme step of confronting his king. It is only in part, however, a political study. In seeking to understand the motives that lay behind their public actions, the book scrutinizes the earls’ private affairs. It establishes for the first time the precise extent of their landed estate, the size of their incomes, and the membership and quality of their affinities. It also examines their relationships with friends and relatives, their building works, and even their personalities. Extensive use is made throughout of unpublished manuscript sources: in particular, the hundreds of ministers’ accounts that have survived from the administration of Roger IV Bigod, and the charters given by both earls, which are calendared and translated in an appendix.