Christianity had first come to Britain during the time of the Roman Empire. With the decline of the empire and the subsequent invasions, Anglo-Saxon Britain had reverted to paganism. In Ireland and Scotland, however, Christianity survived and continued, although separated from the Church in mainland Europe. This isolation led to the Celtic Church developing its own traditions, most notably in the calculation of the date of Easter.

Almost nothing is known of Aidan’s early life save that he was Irish. He is believed to have been a monk who may have studied under Saint Senan on Scattery Island, County Clare in Ireland, but moved to St Columba’s monastery on the Scottish island of Iona in 630 AD.

Edwin was king of Northumbria and had been converted to Christianity in 627 AD by a mission from Canterbury led by Bishop Paulinus. Edwin was killed in battle against invaders from Mercia in 632 AD and Northumbria returned to paganism. At this time, Edwin’s nephew, Oswald, was living in exile in the monastery on Iona. During his stay at the monastery, Oswald was converted and baptised. In 633 AD Oswald regained the kingdom of Northumbria and afterwards sent requests to Iona, rather than Canterbury, for missionaries to convert his people.
The first monk sent to preach in Northumbria, a man named Corman, returned to Iona having had little or no success and complaining that the Northumbrian Saxons were “a savage and unteachable race”. At this Aidan is said to have commented, “Perhaps you were too harsh with them and they might have responded to a gentler approach.” Aidan duly found himself selected to lead a new mission!

Oswald gave Aidan the island of Lindisfarne, sometimes called Holy Isle, on which he established a monastery. Lindisfarne was close to Oswald’s royal palace at Bamburgh. This made it more suitable for the evangelisation of Oswald’s kingdom (Bernicia) in northern Northumbria, than was York, farther to the south.

Initially, Aidan concentrated his missionary work on Oswald’s kingdom, with Oswald himself often acting as Aidan’s interpreter. Later Aidan founded churches and monasteries, freeing slave boys and training them to serve in the church. He encouraged the laity to follow monastic practices such as fasting and meditation on the Gospels and lived himself in poverty. With Oswald’s death in 642 AD, Aidan became friends with Oswin, the king of the southern Northumbrian kingdom of Deira. Some report that Aidan extended his mission even further afield — through the Midlands and even as far as London.

From Bede’s Life of St Cuthbert Aidan died on 31 August 651 AD at Bamburgh. His body was taken to Lindisfarne and buried in the cemetery. Some time later, his bones were removed to the monastery church. Lindisfarne was sacked by the Vikings in 793 AD, after which Aidan’s reputation diminished somewhat. However, St Bede thought very highly of Aidan, perhaps more than of any other saint, and wrote of him:

“He neither sought nor loved anything of this world, but delighted in distributing immediately to the poor whatever was given to him by kings or rich men of the world. He traversed both town and country on foot, never on horseback, unless compelled by some urgent necessity. Wherever on his way he saw any, either rich or poor, he invited them, if pagans, to embrace the mystery of the faith; or if they were believers, he sought to strengthen them in their faith and stir them up by words and actions to alms and good works.”

- StBede