About the year 684, King Ecgfrid of Northumbria made a descent upon the Irish coast, between Magh Breg, the plain north of the Liffey, and Belach Dúinn, now Castlekieran, north-west of Kells, and carried away many captives. In the following year he invaded the Picts of Scotland, and was slain at Dun Nechtan. His successor, Aldfrid (the son, according to some accounts, of an Irish mother), had been driven into exile in early youth, and taking refuge in Ireland was educated in the schools of that country, to which he paid a grateful tribute in after-life. He had sojourned for a while at Iona, and there became acquainted with Adamnán, who now took advantage of this intimacy, and came to Aldfrid’s court to plead the cause of the captives. He was successful in this, and had the happiness to redeem from slavery sixty of his countrymen, whom he brought back with him on his return. This visit produced results of great importance to the Irish Church. During his stay in Northumbria, Adamnán contracted a close intimacy with the Venerable Bede--who strongly censured Ecgfrid’s unprovoked, aggression (_Hist. Eccl._ iv. 26)--upon whom he made a strong and favourable impression, as being _vir bonus, et sapiens, et scientia scripturarum nobilissime instructus_. Their frequent colloquies during this, and, apparently, a second mission of Adamnán to Northumbria, about two years later, turned upon the two main points wherein the Irish usage differed from that of Rome: _i.e._ the form of the tonsure, which, in Ireland, was made crescent-wise across the head, and the time of keeping Easter. In the latter respect, Ireland retained the older computation, founded upon the Jewish method of calculating the Passover, which had been adopted by Rome during the disputes on the subject with the East and with Alexandria, and was in force at the conversion of Ireland. In 463 Pope Hilarius introduced an improved system of calculation, which ultimately was generally adopted throughout the West, though not without a struggle in those many parts of the Continent where Irish influence was powerful. As a matter of course, the reformed system was brought into England by Augustine, and contributed to widen the gulf between the English and British Churches. The south of Ireland, or part of it, appears to have accepted the change in the year 633, but it took nearly another century to win over the rest of the country. Bede urged upon Adamnán the propriety of conforming to the general rule of the Church, and his arguments wrought such conviction in his hearer that Adamnán devoted much of the latter portion of his life to the task of inducing his countrymen to accept the Roman usage.