The exact terms of the treaty between William’s royal vassal and his overlord are unknown.  But one of them was clearly the removal of Edgar from Scotland.  Before long he was on the continent.  William had not yet learned that Edgar was less dangerous in Britain than in any other part of the world, and that he was safest of all in William’s own court.  Homage done and hostages received, the Lord of all Britain returned to his immediate kingdom.  His march is connected with many legendary stories.  In real history it is marked by the foundation of the castle of Durham, and by the Conqueror’s confirmation of the privileges of the palatine bishops.  If all the earls of England had been like the earls of Chester, and all the bishops like the bishops of Durham, England would assuredly have split up, like Germany, into a loose federation of temporal and spiritual princes.  This it was William’s special work to hinder; but he doubtless saw that the exceptional privileges of one or two favoured lordships, standing in marked contrast to the rest, would not really interfere with his great plan of union.  And William would hardly have confirmed the sees of London or Winchester in the privileges which he allowed to the distant see of Durham.  He now also made a grant of earldoms, the object of which is less clear than that of most of his actions.  It is not easy to say why Gospatric was deprived of his earldom.  His former acts of hostility to William had been covered by his pardon and reappointment in 1069; and since then he had acted as a loyal, if perhaps an indiscreet, guardian of the land.  Two greater earldoms than his had become vacant by the revolt, the death, the imprisonment, of Edwin and Morkere.  But these William had no intention of filling.  He would not have in his realm anything so dangerous as an earl of the Mercian’s or the Northumbrians in the old sense, whether English or Norman.  But the defence of the northern frontier needed an earl to rule Northumberland in the later sense, the land north of the Tyne.  And after the fate of Robert of Comines, William could not as yet put a Norman earl in so perilous a post.  But the Englishman whom he chose was open to the same charges as the deposed Gospatric.  For he was Waltheof the son of Siward, the hero of the storm of York in 1069.  Already Earl of Northampton and Huntingdon, he was at this time high in the King’s personal favour, perhaps already the husband of the King’s niece.  One side of William’s policy comes out here.  Union was sometimes helped by division.  There were men whom William loved to make great, but whom he had no mind to make dangerous.  He gave them vast estates, but estates for the most part scattered over different parts of the kingdom.  It was only in the border earldoms and in Cornwall that he allowed anything at all near to the lordship of a whole shire to be put in the hands of a single man.  One Norman and one Englishman held two earldoms together; but they were earldoms far apart.