In England, William had a unique opportunity to wipe the slate clean and to modify the Norman-French feudal system to his own liking. It was almost inevitable that he should continue the system, for he and his followers had known no other. Furthermore, the only thing he possessed wherewith to reward his avaricious men was land; and he needed from them the feudal return of military service, to garrison the conquered country. Consequently, he claimed that the Conquest gave him title to the estates of all Anglo-Saxons.
(from A History of England and the British People. Shades of Robin Hood, huh? No wonder the Saxons hated the Normans!)