Aidan was an Irish monk of Iona who was sent at the request of King Oswald of Northumbria — who had been baptized at Iona during his exile — to evangelize his kingdom. Around 635 Aidan arrived in Northumbria and chose as his episcopal seat the tiny tidal island of Lindisfarne off the Northumbrian coast, a few miles from the royal fortress of Bamburgh.
From Lindisfarne — accessible by foot at low tide and cut off by sea at high tide — Aidan walked through the Northumbrian villages, preaching, teaching, founding small churches, and training a generation of Anglian Christians (including the boy who would become St. Cuthbert). King Oswald often translated for him in his early years, as the king had learned Irish at Iona while Aidan was still learning English.
Bede the Venerable (Eccl. Hist. III) gives him one of the most affectionate biographies in his History — a portrait of evangelical poverty, humility, and tireless walking. When King Oswine of Deira gave him a fine horse, Aidan immediately gave it to a beggar; reproved, he answered: 'Is this child of a mare more precious to you than that child of God?'
He died standing against the west wall of a church at Bamburgh, leaning on a buttress, while the king's hall blazed nearby — quenched, by Bede's account, in the moment of his death. Lindisfarne under his successors became the principal monastic and missionary center of the Anglo-Saxon north.