Amazing, as it may seem, England was not always Christian. We do know that there was a Christian presence there before the Roman withdrawal of the Legions in the early 300's. Some scholars feel that travelers from the eastern half of the Empire had introduced Christianity initially, and then it spread among the native Celtic peoples of the island group. Celtic Christianity had its own distinctive variations, and Greek scholarship flourished in Ireland for several centuries after it had died elsewhere in Western Europe.
In the 400's non-Christian Germanic tribes invaded Britain: the Angles, Saxons, and Jutes. They conquered the native Celtic Christians or drove them north and west into Cornwall, Wales, Scotland, and Ireland. In spite of the destruction of their world, Celtic Christian missionaries returned to England to preach the Gospel to the Pagans who had conquered them. To make a link to modern readers, here is a question, could Evangelicals do the same should a "Hispanic Horde" "conquer" the USA? I wonder if love would be our motivation.
On their way, they lost heart and in fear Augustine went back to Rome from Provence and asked that the mission be given up. The Pope, however, commanded and encouraged them to proceed, and they landed in Kent (the southeast corner of England) in 597, and the king, whose wife was a Christian, allowed them to settle and preach.
King Ethelbert's wife, Queen Bertha, daughter of Charibert, one of the Merovingian kings of the Franks, had brought a chaplain with her (Liudhard) and either built a church, or restored a church in Canterbury from Roman times. King Ethelbert himself was a pagan, but allowed his wife to worship God her own way. Probably under influence of his wife, Ethelbert asked Pope Gregory I to send missionaries. This world may never know the influence this godly woman had on subsequent history.
Their preaching was outstandingly successful, the people were hungry for the Good News of salvation, and they made thousands of converts in a short time. In 601 the King Ethelbert himself was converted and baptized. Then Augustine was consecrated bishop and established his headquarters at Canterbury. From his day to the present, there has been an unbroken succession of archbishops of Canterbury.
In 603, Augustine tried to unite the local Celtic Church with Rome, but without much success. There hadn't been much in the way of cooperation along these lines during the whole of his time in England. Old attachments to provincial customs and practices were simply too ingrained. However, with Canterbury firmly established as the ecclesiastical center of England, use of the Roman Rite and calendar would, after his death be universally accepted.
O Lord our God, Who by Your Son Jesus Christ called Your apostles and sent them forth to preach the Gospel to the nations: We bless Your holy name for Your servant Augustine, first Archbishop of Canterbury, whose labors in propagating Your Church among the English people we commemorate today; and we pray that all whom You call and send may do Your will, and bide Your time, and see Your glory; through Jesus Christ our Lord, Who lives and reigns with You and the Holy Spirit, one God, for ever and ever. Amen.