The greatness of Kent did not endure long after the landing of Augustine, for in 616 Ethelbert, who had been over-king of the whole of England as far north as the Humber, died; and his son Eadbald proved an inferior ruler, and even relapsed into paganism. It was to the north that the balance of power now inclined, where Edwin of Deira became King of Northumbria, having overthrown his rival, Ethelfrith of Bernicia, in a great battle, on the banks of the Idle (617). His marriage with Ethelberga, the daughter of Ethelbert of Kent, led to the conversion of Northumbria to Christianity. She brought with her a priest named Paulinus, and he rapidly succeeded in persuading the people to adopt Christianity. The story of the king taking counsel with his aldermen and wise men concerning the new faith which was preached in their midst, and the fine speech made by one of the thegns, in which he compared the life of man to the flight of a sparrow from the darkness into a warm room at wintertime, and thence out into the darkness and storm again, is told us by Bede in his _Ecclesiastical History of the Nation of the English_. "So it is," said the noble, "with the life of man; it endures but for a moment, and we know not at all of what goeth before it and what cometh after it. Therefore, if these strangers can tell us anything that we may know whence a man cometh, and whither he goeth, let us hear them and follow their law." So Northumbria became Christian for the time being, and a church was built at York with Paulinus as its bishop. But in 633 Edwin was defeated and slain at Heathfield by the King of the Welsh, and Penda the heathen king of Mercia, and the country relapsed for a time into heathendom, until Oswald, Edwin's nephew, known as St. Oswald, brought St. Aidan, a Scottish bishop, to Northumbria, and founded the see of Lindisfarne, in Holy Island, off the Northumbrian coast. There the holy St. Cuthbert lived, until his death in 687, and, going forth over all Northumbria, converted vast numbers of men and women. Concerning the conversion of the remaining kingdoms, we know comparatively little. Mercia became Christian on the death of Penda, who was overthrown by Oswy of Northumbria, in 655, at the battle of Winwood. Wessex was converted by a bishop called Birinus, who was sent from Rome by Pope Honorius; and though the first bishopric was fixed at Dorchester, in Oxfordshire, the episcopal seat of Wessex was eventually fixed at Winchester, and Dorchester became that of the Mercians. The last part of England to become Christian was East Anglia, which was converted by Wilfrith, who had been driven from Northumberland by King Egfrith, Oswy's son and successor.