History of England, Medieval Britain - Henry II, Richard I, John I

"Showing not a sign of his willingness to honor the compromise, Becket immediately excommunicated the Archbishop of York and the other bishops who had assisted at the coronation of Henry's oldest son. When the news reached Henry in Normandy, his anger was uncontrollable and the four knights who sped to Canterbury to murder Becket in his own cathedral thought that this was an act desired by the King. Instead, the whole of Europe was outraged.

The dead archbishop was immensely more powerful than the live one, and more than Henry's abject penance made the murdered Becket the most influential martyr in the history of the English Church."

snip