The Synod of Whitby of 664 forms a significant watershed in that King Oswiu of Northumbria decided to follow Roman rather than Celtic practices, but the two rites co-existed for another century, Wales observing the Celtic Easter date until 768.
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Bede portrays Cælin as a chaplain at the court of Ethelwald, a nephew of King Oswiu of Northumbria.
Osric, the nephew of Edwin, ruled Deira after Edwin, but his son Oswine was put to death by Oswiu in 651.