Knighted in , William Marshal spent his younger years as a knight errant and a successful tournament competitor; Stephen Langton eulogised him as the "best knight that ever lived.
The title of earl was not officially granted until , and is considered to be the second creation of the Pembroke earldom.
Just before his death, he fulfilled a promise he said he made in his youth while on crusade by taking vows as a Knight Templar , and was buried in the Temple Church in London. Before William, his father's family held a hereditary title of Marshal to the King , which by his father's time had become recognised as a chief or master Marshalcy, involving management over other Marshals and functionaries.
William became known as "the Marshal", although by his time much of the function was delegated to more specialised representatives as happened with other functions in the King's household. Because he was an earl, and also known as the marshal, the term " earl marshal " was commonly used and this later became an established hereditary title in the English peerage. William's father, John Marshal , supported King Stephen when Stephen took the throne in , but in about he changed sides to support the rival claimant Empress Matilda in her war of succession against Stephen, which led to the collapse of England into a year civil war known as " the Anarchy ".
When King Stephen besieged Newbury Castle in , according to William's biographer, he used the young William as a hostage to ensure that John kept his promise to surrender the castle. John, however, used the time allotted to reinforce the castle and to alert Matilda's forces.
