We need not enter into the details of the long struggle between Canterbury and York. The archbishopric of Canterbury was vacant for five years after the death of Anselm; its revenues went to support the various undertakings of the king. In April, 1114, Ralph of Escures, Bishop of Rochester, was chosen Anselm's successor. The archbishopric of York had been vacant only a few months, when it was filled, later in the summer, by the appointment of Thurstan, one of the king's chaplains. The question of the obligation of the recently elected Archbishop of York to bind himself to obedience to the primate of Britain, whether settled as a principle or as a special case, by an English council or by the king or under papal authority, arose anew with every new appointment. In the period which follows the appointment of Thurstan, a new element of interest was added to the dispute by the more deliberate policy of the pope to make use of it to gain a footing for his authority in England, and to weaken the unity and independence of the English Church. This attempt led to a natural alliance of parties, in which, while the issue was at bottom really the same, the lines of the earlier investiture conflict were somewhat rearranged. The pope supported the claim of York, while the king defended the right of Canterbury as bound up with his own.

At an important meeting of the great council at Salisbury, in March, 1116, the king forced upon Thurstan the alternative of submission to Canterbury or resignation. The barons and prelates of the realm had been brought together to make formal recognition of the right to the succession of Henry's son William, now fourteen years of age. Already in the previous summer this had been done in Normandy, the barons doing homage and swearing fealty to the prince. Now the English barons followed the example, and, by the same ceremony, the strongest tie known to the feudal world, bound themselves to accept the son as their lord on the death of his father. The prelates, for their part, took oath that if they should survive Henry, they would recognize William as king, and then do homage to him in good faith. The incident is interesting less as an example of this characteristic feudal method of securing the succession, for this had been employed since the Conquest both in Normandy and in England, than because we are told that on this occasion the oath was demanded, not merely of all tenants in chief, but of all inferior vassals. If this statement may be accepted, and there is no reason to doubt it, we may conclude that the practice established by the Conqueror at an earlier Salisbury assembly had been continued by his sons. This was a moment when Henry was justified in expressing his will, even on a matter of Church government, in peremptory command, and when no one was likely to offer resistance. Thurstan chose to surrender the archbishopric, and promised to make no attempt to recover it; but apparently the renunciation was not long regarded as final on either side. He was soon after this with the king in Normandy, but he was refused the desired permission to go to Rome, a journey which Archbishop Ralph soon undertook, that he might try the influence of his presence there in favour of the cause of Canterbury and against other pretensions of the pope.

From the date of this visit to Normandy, in the spring of 1116, Henry's continental interests mix themselves with those of the absolute ruler of the English Church, and he was more than once forced to choose upon which side he would make some slight concession or waive some right for the moment. Slowly the sides were forming themselves and the opposing interests growing clear, of a great conflict for the dominion of northern France, a conflict forced upon the English king by the necessity of defending the position he had gained, rather than sought by him in the spirit of conquest, even when he seemed the aggressor; a conflict in which he was to gain the victory in the field and in diplomacy, but to be overcome by the might of events directed by no human hand and not to be resisted by any.

The peace between Henry and Louis, made in the spring of 1113, was broken by Henry's coming to the aid of his nephew, Theobald of Blois. Theobald had seized the Count of Nevers on his return from assisting Louis in a campaign in the duchy of France in 1115. The cause was bad, but Henry could not afford to see so important an ally as his nephew crushed by his enemies, especially as his dominions were of peculiar strategical value in any war with the king of France. To Louis's side gathered, as the war developed, those who had reason from their position to fear what looked like the policy of expansion of this new English power in north-western France, especially the Counts of Flanders and of Anjou. The marriage of Henry's son William with Fulk's daughter had not yet taken place, and the Count of Anjou might well believe - particularly from the close alliance of Henry with the rival power of Blois - that he had more to fear than to hope for from the spread of the Norman influence. At the same time the division began to show itself among the Norman barons, of those who were faithful to Henry and those who preferred the succession of Robert's son William; and it grew more pronounced as the war went on, for Louis took up the cause of William as the rightful heir of Normandy. In doing this he began the policy which the French kings followed for so many years, and on the whole with so little advantage, of fomenting the quarrels in the English royal house and of separating if possible the continental possessions from the English.