In 595, Pope Gregory I (Saint Gregory the Great) decreed a mission be sent to convert the Anglo-Saxons to Britain. The Roman legions had departed from Britannia in 410 and pagan tribes had settled into the land, especially in the southern parts. Until the mission ordered by Pope Gregory no attempts by the native Christians remaining in Britain had attempted to convert the Anglo Saxons. The target kingdom for this mission was the Kingdom of Kent for several factors, most notably that the King Aethelberht had recently married a Christian princess by the name of Bertha (whom was the daughter of Charibert I, a Merovingian king of the Franks). Kent was also the dominant power in Southeastern Britain.
At the time, Saint Augustine was the prior of the Abbey of Saint Andrew's in Rome. After being selected to lead the mission, several other monks were chose to accompany him and received help, supplies and additional priests from the Frankish kings and bishops. Saint Augustine was selected for his deep and extensive knowledge of the Bible and his administrative abilities at the Abbey. After leaving Rome, the missionaries halted in Italy as the task ahead of them began to truly set in. For two years they sent letters back and forth and the group finally arrived in Kent in 597.
King Aethelberht allowed the missionaries to settle and they began to preach in the capital of the kingdom, Canterbury. Within the first year of his arrival, hundred had converted likely including the King himself as it was generally traditional for the ruler of a people to convert first during the early medieval period. His baptism likely also took place in Canterbury. After this large initial success Saint Augustine established his episcopal see at Canterbury though the exact date of Saint Augustine's consecration to Bishop has been lost. The Venerable Bede writes that it likely happened after the conversion of the King by the Frankish Archbishop Aetherius of Arles.
King Aethelberht donated land to Saint Augustine and on which the monastery of Saints Peter and Paul was founded (it would later be named Saint Augustine's Abbey). Additional missionaries arrived in 601 from Rome and brought with them a pallium for Saint Augustine, sacred vessels, vestments, relics and books. The pallium was accompanied by Saint Pope Gregory instructing Saint Augustine to consecrate 12 suffragan bishops and soon as possible and to send a bishop to York so that there wound be two metropolitans with 12 suffragan bishops under each. In 604 Saint Augustine founded two more bishoprics in Britain with the consecration of Mellitus as the Bishop of London and Justus as the Bishop of Rochester.
Pagan temples were soon consecrated for use in the Christian church and feasts were moved to dates that celebrated Christian martyrs. To prevent political clashes Saint Pope Gregory placed the mission in Britain under Papal authority - English bishops would not have authority over Frankish counterparts and Frankish no authority over English. Saint Augustine founded The King's School in Canterbury which makes it the oldest existing school.
Saint Augustine of Canterbury died on May 26th, 604 shortly after naming Laurence of Canterbury as his successor to ensure a smooth transition of office. He was originally buried in the portico of what is now Saint Augustine's Abbey in Canterbury but was later exhumed and placed inside a tomb within the Abbey Church. After the Norman conquest his shrine at the Abbey held a central position in one of the axial chapels. King Henry I granted the abbey a six day air from September 8th to September 13th.
Today his feast day is celebrated as an optional memorial for May 27th.