The Anglo-Saxons A History of the Beginnings of England: 400–1066

by Marc Morris

At the same time, the vikings in the Irish Sea zone were growing in power and confidence. Iona, the most venerable of all the Gaelic monasteries, was raided for a second time in 802, and a third in 806, on which occasion sixty-eight members of the community were killed. When the raiders returned for a fourth time the following year, most of the survivors decided that enough was enough, and that the isolated site selected by St Columba in the sixth century was simply too vulnerable in the new conditions of the ninth. At that point they relocated to Ireland, re-founding a monastery at Kells that was located on the site of an ancient hill fort, over twenty miles from the sea.