The years between 1258 and 67 comprise one of the most influential periods in the Middle Ages in England. This turbulent decade witnessed a bitter power struggle between King Henry III and his barons over who should control the government of the realm. Before England eventually descended into civil war, a significant proportion of the baronage had attempted to transform its governance by imposing on the crown a programme of legislative and administrative reform far more radical and wide-ranging than Magna Carta in 1215. Constituting a critical stage in the development of parliament, the reformist movement would remain unsurpassed in its radicalism until the upheavals of the seventeenth century. Simon de Montfort, the baronial champion, became the first leader of a political movement to seize power and govern in the king's name. The essays collected here offer the most recent research into and ideas on this pivotal period. Several contributions focus upon the roles played in the political struggle by particular sections of thirteenth-century society, including the Midland knights and their political allegiances, aristocratic women, and the merchant elite in London. The events themselves constitute the second major theme of this volume, with subjects such as the secret revolution of 1258, Henry III's recovery of power in 1261, and the little studied maritime theatre during the civil wars of 1263-7 being considered.