King John of England's expulsion of the monks from Canterbury marked a pivotal moment in his contentious relationship with the Church. The underlying cause of this drastic measure was the monks' support for Stephen Langton, who was appointed archbishop by Pope Innocent III, a decision that King John vehemently opposed. The king sought to maintain control over ecclesiastical appointments, asserting his authority in a realm that he feared could undermine his power.

The Canterbury monks, loyal to the pope and supportive of Langton, became targets of John's ire. On July 15, 1207, he ordered their expulsion from the priory, creating an immediate vacuum in the monastic leadership at one of England's most important cathedrals. This act was not merely a personal vendetta; it signified a broader struggle between the monarchy and the papacy, highlighting the tension between secular and ecclesiastical powers during this period.

The expulsion was emblematic of the larger conflict known as the Interdict, wherein Pope Innocent III imposed an interdict on England in response to John's disregard for the pope's authority. The interdict essentially suspended all ecclesiastical functions, denying spiritual services to the populace. This resulted in widespread frustration among the people, amplifying dissent against the king's heavy-handed governance. The overall impact of this conflict continued to reverberate through English politics and society, ultimately contributing to the seeds of discontent that would culminate in the Magna Carta in 1215.