William Marshal (or William the Marshal) (c.1147-1219) was the fourth son of a minor lord who had the hereditary title of “lord marshal”. He rose to become the most powerful man in England as the regent for the young Henry III.
As a younger son he was due no inheritance and was dependent entirely on his own wits to make his way in the world. His martial prowess and strength of character impressed Eleanor of Aquitaine who appointed him guardian of her eldest son, “Henry the Young King”. As such he was involved in the almost ceaseless conflict between Henry II and his quarrelsome sons, but managed to retain the respect of all sides. On Henry’s death in 1183 William went on crusade to the Holy Land.
In 1189 the recently crowned Richard I gave him the heiress Isabella of Pembroke in marriage, suddenly giving him the wealth and station to match his personal prestige. During Richard’s absence in Palestine and later incarceration William was instrumental in keeping younger brother John’s excesses to a minimum, but on Richard’s death in 1199 he gave his support to John as king. He was a leading instigator in getting John and the barons together at Runnymede for the signing of the Magna Carta.
When John died in 1216 William was made Regent for the young Henry III leading the English forces against an invading French army and secured the kingdom. He died in 1219, after a long and meritorious career, having served four kings.
Reference: The Plantagenet Encyclopedia.