The political history of William's later years is unimportant; his main energy was absorbed in the task of holding down and organizing his new kingdom. His rather precarious conquest of the county of Maine, his long quarrels with Philip I of France, who suborned against him his undutiful and rebellious eldest son Robert, his negotiation with Flanders and Germany, deserve no more than a mention. It is more necessary to point out that he reasserted on at least one occasion (when King Malcolm Canmore did him homage) the old suzerainty of the English kings over Scotland. He also began that encroachment on the borders of Wales which was to continue with small interruptions for the next two centuries. The advance was begun by his great vassals, the earls of Chester, Shrewsbury and Hereford, all of whom occupied new districts on the edge of the mountains of Powys and Gwynedd. William himself led an expedition as far as St. Davids in 1081, and founded Cardiff Castle to mark the boundary of his realm north of the Bristol Channel.
Perhaps the most noteworthy event of the second portion of the Conqueror's reign was a rebellion which, though it made no head and was easily suppressed, marks the commencement of that feudal danger which was to be the constant trouble of the English kings for the next three generations. Two of the greatest of his foreign magnates, Roger, Earl of Hereford, and Ralph, Earl of Norfolk, rose against him in 1075, with no better cause than personal grievances and ambitions. He put them down with ease; the one was imprisoned for life, the other driven into exile, while Waltheof, the last of the English earls, who had dabbled in a hesitating way in this plot, was executed.
There was never any serious danger, but the fact that under the new regime baronial rebellion was possible, despite of all William's advantages over other feudal kings, and despite of the fact that the rebels were hardly yet settled firmly into their new estates, had a sinister import for the future of England. With the new monarchy there had come into England the anarchic spirit of continental feudalism. If such a man as the Conqueror did not overawe it, what was to be expected in the reigns of his successors? William had introduced into his new realm alike the barons, with their personal ambition, and the clerics of the school of Hildebrand, with their intense jealousy for the rights of the church. The tale of the dealings of his descendants with these two classes of opponents constitutes the greater part of English history for a full century.
Text extracted from the entry for ENGLISH HISTORY in the 1911 Encyclopedia Britannica, the text of which lies within the public domain.