Put simply, Henry II believed that Thomas was the best man for the job. The relationship between the monarch and the church was always a slightly awkward one at this point in history, with the balance of power and the boundaries between the two never quite resolved. Thomas Becket had been Henry II's chancellor and done an excellent job in this role. Moreover, he was also Henry's friend. It is likely that Henry believed that Thomas would not only serve the English church well, but that he was also the candidate most likely to see eye-to-eye with the king over matters that might otherwise prove fractious, particularly over how to deal with criminous clerks.
Unfortunately, all the biographers agree that Thomas, once consecrated, put off the chancellor and put on the archbishop. On moving from the court to the church, some change was of course necessary. Thomas had a new office and a completely new set of duties. He was not only new to the archbishopric but also to the priesthood, the celebration of Mass and the act of ordination. William of Canterbury says that Thomas asked Henry to appoint a new chancellor when he found that his pastoral duties were too heavy to allow him to serve two masters. There is some truth in this as unless Thomas was to remain a member of the royal household and follow the royal itinerary, he would probably have been able to retain the chancellorship in some titular or honorary capacity only. Moreover, as archbishop, Thomas would have had no need of the office of Chancellor which would now bring in little revenue, and which he may have considered beneath his dignity. Guernes embroiders William of Canterbury’s account by making Thomas send Master Ernulf to return the great Seal to Henry who was greatly offended. Thomas’ biographers regarded his change of life-style as the direct cause of his quarrel with the king: as he began to observe the laws of God he was forced to disobey the royal laws. This interpretation is too simplistic, however.
The problem really lies in Thomas’ attraction to extremes. It could be argued that he was a perfectionist. He had been the perfect chancellor, and now he was attempting to be the perfect archbishop. Compelled by his own sense of unworthiness and admitted episcopal deficiencies, he was determined to out-bishop the rest. Added to this dangerous motivation could be added the fact that the archbishopric had given Thomas an independent power base. He no longer needed to be a courtier and his pride, even if now put to the service of the church, gave him an audacity unbearable to the strong-willed and quick-tempered king. Herbert of Bosham maintains that Thomas would have no clerk in his household who had sworn fealty to the king. He required undivided loyalty, and when Henry’s patience ran out there would certainly be a great deal of trouble.