Final answer:
The pallium given to St. Augustine of Canterbury by Pope St. Gregory the Great was a symbol of authority and ecclesiastical jurisdiction, reinforcing the Pope's role in missionary expansion and church influence in the Christianization of England.
Step-by-step explanation:
When St. Augustine of Canterbury was given a pallium by Pope St. Gregory the Great, it symbolized the granting of authority and recognition of Augustine as the leader of the church in England. The pallium, a cloak-like garment, was a significant vestment that marked the wearer as an archbishop with certain jurisdictional powers. Pope Gregory the Great's decision to confer the pallium on Augustine underscored the Pope's role in overseeing the expansion of Christian missionary work and the spreading of Christianity throughout Europe, and it demonstrated a strategic move in creating bonds with burgeoning Christian realms. It also reflected the political realities of the time where the church was asserting its influence amidst tangled relationships with monarchs and rulers.