William de Lanvallei  William de Lanvallei III (died 1217) was an English landowner, governor of Colchester Castle, and a "Magna Carta" surety. He was lord of Walkern. William III accompanied King John of England on his expedition to Poitou in 1214 and was present at the truce. William III was related to several of the "Magna Carta" barons. William III's grandfather, William I (1125-1180), was an administrator for Henry II of England and came to England from Brittany. William I married Gunnora, the daughter of Hubert de Saint Clair (1120-1155). William II (c.1161-1204), son of William I, married Hawise, great-granddaughter of Hugh de Bocland (Buckland, Oxfordshire). William III, son of William II, married Maud, daughter of Gilbert (Hamon) Peche. Maud was niece of Robert Fitzwalter, a leader of the "Magna Carta" barons. Hawise, daughter of William III, was placed as ward with Hubert de Burgh . Hubert married Hawise to his son, John.