Saint Aiden founded the Priory at Lindisfarne in 634 AD. Aiden was an Irish Monk who came to Northumbria of King Oswald to convert the Northumbrians to Christianity. Saint Aiden converted the Anglo-Saxon pagens with "...the milk of gentle doctrine, to bring them by degrees, while nourishing them with the Divine Word, to the true understanding and practice of the more advanced precepts." Any money he and his brothers received from the great and powerful was distributed to the poor and so earned a reputation of pious and humble charity. He died in 651.
Celtic Christianity was distinct from "Roman" or "Catholic" Christianity in certain practices and traditions such as the dating of Easter, style of monastic tonsure, system of penance, permeable monastacism, babtismal rites, and the preference of the Rules of Saint Columbanus. Even though the Priory of Lindisfarne had a tradition of asceticism, Celtic Christianity at the time allowed it's nuns and priests to marry and have children.
The beginning of the Viking age was ushered in with the raid on Lindisfarne in 793 AD.
"On the seventh of the ides of June, they reached the church of Lindisfarne, and there they miserably ravaged and pillaged everything; they trod the holy things under their polluted feet, they dug down the altars, and plundered all the treasures of the church. Some of the brethren they slew, some they carried off with them in chains, the greater number they stripped naked, insulted, and cast out of doors, and some they drowned in the sea." ~ "History of the Church of Durham" by the Monk Simeon (of Durham).