Whitby, Synod of, 664. The Northumbrian church, which began with Paulinus and Roman Christianity, was revived by Aidan, who introduced Celtic customs from Iona. The most controversial difference, the dating of Easter, was the main issue at Whitby. Bede highlights the inconvenience when King Oswiu's Celtic Easter conflicted with his queen Eanflæd's Roman observance. As the dates rarely diverged, it is possible the debate was prompted by political tension between Oswiu and his son Alhfrith, subking of Deira. Influenced by Wilfrid, whom he made abbot at Ripon, expelling Celtic adherents, Alhfrith had recently adopted Roman practices.

Key Northumbrians representing the Celtic cause at Whitby were Abbess Hilda, Cedd, bishop to the East Saxons, and Bishop Colman of Lindisfarne. Wilfrid was spokesman for the visiting Frankish bishop Agilbert from Wessex, and his priest Agatho, main advocates for Rome. Oswiu's decision to conform with the greater body of Roman Christianity may have been politically expedient. He probably defused a situation created by Alhfrith, and won vital papal acknowledgement of his supremacy in England. Whitby prepared the way for unification of the English church by Theodore, next archbishop of Canterbury.

Audrey MacDonald

Whitby, Synod of a conference held in Whitby in 664 that resolved the differences between the Celtic and Roman forms of Christian worship in England, in particular the method of calculating the date of Easter. The Northumbrian Christians had followed the Celtic method of fixing the date while those of the south had adopted the Roman system. King Oswy (612–70) of Northumbria decided in favour of Rome, and England as a result effectively severed the connection with the Celtic Church.