‘Will no one rid me of this turbulent priest?’

Answer: King Henry II of England (March 5, 1133 – July 6, 1189)

The Priest in question was Thomas Becket, Archbishop of Canterbury.

Thomas Becket clashed with King Henry II because Thomas sustained that the Pope and English Bishops could not accept the jurisdiction of the King over them. This refusal to submit to the crown provoked Henry to the full force of his Plantagenet anger.

Four of Henry’s knights murdered Becket in order to court favour with him and in doing so turned Becket into a saint. Henry lost popularity and had to become a penitent. He was publicly whipped by monks and made himself wear a horsehair shirt.
Ouch.