William Marshall (the man)
William Marshal (1146-1219) was a man who was barely even noble, but who rose to become one of the most powerful people in the Angevin world. His skill at arms was one source of his renown, being particularly successful at Tourney. He was the son of John Fitzgilbert and one Aline Pipard, and the Marshal of England for a number of kings (as had been his father, his grandfather Gilbert, and his great-grandfather geoffrey) and he fought in the Middle East as a Knight Templar. He is often held up to be a shining example of chivalry, but some historians claim that the evidence indicates that he was ruthless, pragmatic and manipulative.
He became chivalric lord to Henry II's son, the Young King, and was granted the fief of Cartmel in Lancashire in 1187. After the Young King died he went to the Holy Land, and on his return became Henry's Marshal. When Henry died, his son Richard recognised William's worth (despite Marshal having unhorsed him protecting Henry in France from a revolt of Richard's) and saw to his making a good marriage.
He married Isobel de Clare, inheriting thereby the de Clare lands of ehr father Richard 'Strongbow', in Pembroke and Striguil (english: Chepstow)
His son, William II, had a biographical text written L' Historie de Guillaume le Marechal.
William Marshal (event)
A Stormhold event held every year, usually on the first Saturday of December. It is in honour of William Marshall, the man. There is usually a chivalric weapons tourney, and a ransom melee followed by an elaborate feast with an early period theme. It is one of the two "high" events held annually in Stormhold, the other being Winter Feast.
It's the type of event that people who don't attend SCA events often come out of the woodwork for, and people wear try to wear their best garb, especially Angevin garb. It's just another excuse to make another piece of garb.