Meeting of the Christian church of the Anglo-Saxon kingdom of Northumbria in 664 or, possibly, 663, to decide whether to follow Celtic or Roman usages, which had been reintroduced to southern England by St. Augustine of Canterbury in 597. Though Northumbria had been mainly converted by Celtic missionaries, the king decided for Rome, believing that Rome followed the teaching of St. Peter, holder of the keys to heaven. The decision contributed to the unification of the English church and brought it into close contact with the rest of Europe