William of Champvent or Guillaume de Champvent was the son of Henri, Lord of Champvent, brother of Othon de Champvent and Pierre de Champvent, cousin of Otto de Grandson. He followed Peter II, Count of Savoy to England and served King Henry III of England as a diplomat. His church career in England, being a dean of St. Martin's Le Grand in London from 1262. His influence at court in 1262 is evidenced by his joining the Savoyard witness list for a charter relating to Queen Alianor’s dowry. Upon his departure back to Lausanne Edward I of England would appoint Louis I of Vaud to St. Martin's Le Grand