William de Valence's dramatic medieval career shaped English and French crises, from Henry III to Edward I. Deeply-researched and very readable 'living history' to catch readers by a stimulating narrative based on best secondary works and original sources in medieval history from clerics and state officials' records and works from contemporary history authors shows William de Valence is an unique source. He was personally involved in the greatest existential crises for the English and French kingdoms and connected sovereignties, Europe to the Middle East and 'outremer' territories of the crusades. On William's arrival in England as the king's half-brother, after elite marriage, he was showered with honours, offices, military and political commands and as Constable of Pembroke Castle served the great warrior king, Edward I, in the conquest of Wales. William's career shows close involvement in the crises of the English state and turbulent reigns of Henry III and Edward I and royal power and magnate opposition during including the fractious Oxford Parliament and Provisions of Oxford, the campaign of Simon de Montford to replace the monarchy, the Second Baron's War and final royal victory at Evesham. William was at the king's side providing counsel, political and miliary support, and none greater than the conquest of Wales. The impressive monument in Westminster Abbey is a lasting tribute to a French-born servant of the English state and monarchy.