Robert was the eldest surviving son of Robert de Beaumont, 3rd Earl of Leicester and Petronilla de Grandmesnil, who was either a granddaughter or great-granddaughter of Hugh de Grandmesnil. Robert had an elder brother but he died in 1189. As a young man, he accompanied King Richard I on the Third Crusade, and it was while the crusading forces rested at Messina, Sicily that Robert was invested with the Earldom of Leicester on 2 February 1191 in Sicily. Robert's newly gained estates included a large part of central Normandy. He held castles at Pacy, Pont-Saint-Pierre and Grandmesnil. Earl Robert also was lord of the vast honor of Breteuil, but the family castle there had been dismantled after the 1173-1174 War. On his return from the crusade, he turned his attentions to the defense of Normandy from the French. After defending Rouen from the advances of Philip II of France, he attempted to retake his castle of Pacy. He was captured by forces of the French king and remained imprisoned for 3 years. Later, King John would bestow the new fortress and lordship of Radepont upon the earl. Sometime after his release in 1196 he married Loretta de Braose, daughter of William de Braose, 4th Lord of Bramber. They had no children, and Robert's death in 1204 brought the end of the Beaumont male line. In the year of his death Normandy was lost to the French; Earl Robert attempted to come to an independent arrangement with King Philip of France, in which he would hold his land in Normandy as a liege-vassal of the Kings of France, and his lands in England as a liege-vassal of the Kings of England. In any event, Robert died on 20 or 21 October 1204, and his large English estates were divided between the heirs of his two sisters. The eldest sister, Amice, had married the French baronSimon de Montfort, and their son, also named Simon de Montfort, inherited half the estate as well as the title of Earl of Leicester. The younger sister, Margaret, had married Saer de Quincy, and they inherited the other half. Three years later Saer was created Earl of Winchester.
