The Manor passed from the Count of Meulan to Henry de Beaumont, 1st Earl of Warwick, who enfeoffed his great-nephew Thurstan, the first of the De Montforts of Beaudesert, and the builder of the castle. About the year 1140, Thurstan obtained from the Empress Matilda the right to hold a market on Sundays at his castle of Beaudesert. He was succeeded by his son Henry, who died in 1191 and then by his son, Thurstan who, dying in 1216, was succeeded by his son Peter, a minor, and who became a ward of William de Cantelupe of Aston Cantlow; it was this association which led him to later side with the Barons. Peter de Montfort became the most powerful of all the de Montforts and in him the family was at the height of its glory. Peter obtained on, 10 February 1227 the grant of a market on Monday and a yearly fair at his manor of Beaudesert to be held on 'the eve, feast, and morrow of St. Giles'. In the Barons' wars he sided against the king, Henry III and was one of those who formulated the Provisions of Oxford in 1258. He was taken prisoner at Northampton, but was released and following the Peace of Canterbury was elected one of the council of nine. He was killed fighting beside his kinsman Simon de Montfort, although the exact relationship is not known, at Evesham in 1265. His eldest son Peter was taken prisoner at Evesham and placed in the custody of Thomas de Clare, to whom his forfeited lands were granted, but shortly afterwards he was pardoned and his lands restored to him. The manor then descended to his son John and then to his son, John who was aged 5 at his father's death, in 1296, and named as heir to the castle of Beaudesert. This John was concerned in the execution of Piers Gaveston, but was afterwards pardoned and died fighting for the king at Bannockburn in 1314.