Thomas Beckett was first a clerk then an archdeacon of Canterbury before Henry II ascended the throne in 1154. Beckett seems to have had an immediate raport with the king who was fourteen years his junior. The two were almost constant companions and within a year Beckett became Henry's chancellor.
When Theobald, the Archbishop of Canterbury, died in 1161 Thomas Beckett was elected to the post at Henry's urging. Signalling that he was to be no mere king's puppet Beckett resigned his post as chancellor against Henry's wishes. A series of conflicts arose between the two, most notably the question of supremacy of the king's courts when dealing with the clergy. By 1163 their mutual hostility was open.
1164 saw the council of Clarendon, which was intended to establish a set of customs to settle church-state disputes. Its constitutions never received Thomas Beckett's seal, and Beckett was to strongly criticise them later. In October of that same year the two men had an angry confrontation in Northampton which led Beckett to flee to France and spend six year in exile.
On his return to England in 1170, Beckett delivered a provocative Christmas speech. When news of this reached the king he was furious. Four knights, who thought they understood the intent behind the king's ranting traveled to Kent and killed Beckett.
His death was naturally considered a martyrdom by the church. Coupled with the fact that the priests who dealt with Beckett's body found a hair shirt underneath his finery, it was only a matter of time before Beckett was made a saint. Canterbury later became a place of pilgrimage, as made famous in the Canterbury Tales.