From "The Origins of Some Anglo-Norman Families":
William of Arques has been the subject of an exhaustive study by Professor D. C. Douglas in the introduction to his edition "The Domesday Monacharum of Christ Church Canterbury", where full references are given to the authorities; and it is unnecessary to go over the ground again. Briefly he held Folkestone, Kent, and was the son of Godfrey Vicomte of Arques. The identity of the tenant of Folkstone is established by the fact that it passed to Nigel de Monville who had married his daughter and coheiress Emma. He must not be confused with William of Arques, a monk of Moleme who was a counsellor of Robert Curthose, and still less with William, count of Arques, the uncle of William the Conqueror. The ruined castle of Arques-la-Bataille is well known.