Peter de Montfort participated in his father's treasons, and was taken prisoner at the Battle of Evesham, but being allowed the benefit of the Dictum of Kenilworth, he was restored to his paternal inheritance, and afterwards enjoyed the favour of Edward I, in whose Welsh wars he took a very active part. He died in 1287, leaving John, his son and heir, and a daughter. He married circa 1260 Maud, daughter and heir of Matthew, son of Henry de la Mare, with whom he had Alstead in Surrey.