We cannot know how or when Christianity first reached Britain, but it was certainly well before Christianity was accepted by the Roman Emperor Constantine in the early fourth century ad. In the last hundred years of Roman government Christianity became firmly established across Britain, both in Roman-controlled areas and beyond. However, the Anglo-Saxons belonged to an older Germanic religion, and they drove the Celts into the west and north. In the Celtic areas Christianity continued to spread, bringing paganism to an end. The map of Wales shows a number of place-names beginning or ending with llan, meaning the site of a small Celtic monastery around which a village or town grew.
In 597 Pope Gregory the Great sent a monk, Augustine, to re-establish Christianity in England. He went to Canterbury, the capital of the king of Kent. He did so because the king's wife came from Europe and was already Christian. Augustine became the first Archbishop of Canterbury in 601. He was very successful. Several ruling families in England accepted Christianity. But Augustine and his group of monks made little progress with the ordinary people. This was partly because Augustine was interested in establishing Christian authority, and that meant bringing rulers to the new faith.
It was the Celtic Church which brought Christianity to the ordinary people of Britain. The Celtic bishops went out from their monasteries of Wales, Ireland and Scotland, walking from village to village teaching Christianity. In spite of the differences between Anglo-Saxons and Celts, these bishops seem to have been readily accepted in Anglo-Saxon areas. The bishops from the Roman Church lived at the courts of the kings, which they made centres of Church power across England. The two Christian Churches, Celtic and Roman, could hardly have been more different in character. One was most interested in the hearts of ordinary people, the other was interested in authority and organisation. The competition between the Celtic and Roman Churches reached a crisis because they disagreed over the date of Easter. In 663 at the Synod (meeting) of Whitby the king of Northumbria decided to support the Roman Church. The Celtic Church retreated as Rome extended its authority over all Christians, even in Celtic parts of the island.
England had become Christian very quickly. By 660 only Sussex and the Isle of Wight had not accepted the new faith. Twenty years later, English teachers returned to the lands from which the Anglo-Saxons had come, bringing Christianity to much of Germany.
Saxon kings helped the Church to grow, but the Church also increased the power of kings. Bishops gave kings their support, which made it harder for royal power to be questioned. Kings had "God's approval". An eldest son did not automatically become king, as kings were chosen from among the members of the royal family, and any member who had enough soldiers might try for the throne. In addition, at a time when one king might try to conquer a neighbouring kingdom, he would probably have a son to whom he would wish to pass this enlarged kingdom when he died. And so when King Offa arranged for his son to be crowned as his successor, he made sure that this was done at a Christian ceremony led by a bishop. It was good political propaganda, because it suggested that kings were chosen not only by people but also by God.
There were other ways in which the Church increased the power of the English state. It established monasteries, or minsters, for example Westminster, which were places of learning and education. These monasteries trained the men who could read and write, so that they had the necessary skills for the growth of royal and Church authority. The king who made most use of the Church was Alfred, the great king who ruled Wessex from 871-899. He used the literate men of the Church to help establish a system of law, to educate the people and to write down important matters. He started the Anglo-Saxon Chronicle, the most important source, together with Bede's Ecclesiastical History of the English People, for understanding the period.
During the next hundred years, laws were made on a large number of matters. By the eleventh century royal authority probably went wider and deeper in England than in any other European country.
This process gave power into the hands of those who could read and write, and in this way class divisions were increased. The power of landlords, who had been given land by the king, was increased because their names were written down. Peasants, who could neither read nor write, could lose their traditional rights to their land, because their rights were not registered.
The Anglo-Saxon kings also preferred the Roman Church to the Celtic Church for economic reasons. Villages and towns grew around the monasteries and increased local trade. Many bishops and monks in England were from the Prankish lands (France and Germany) and elsewhere. They were invited by English rulers who wished to benefit from closer Church and economic contact with Europe. Most of these bishops and monks seem to have come from churches or monasteries along Europe's vital trade routes. In this way close contact with many parts of Europe was encouraged. In addition they all used Latin, the written language of Rome, and this encouraged English trade with the continent. Increased literacy itself helped trade. Anglo-Saxon England became well known in Europe for its exports of woollen goods, cheese, hunting dogs, pottery and metal goods. It imported wine, fish, pepper, jewellery and wheel-made pottery.