In 616, Rædwald defeated and killed Æthelfrith of Northumbria in the Battle of the River Idle and then installed Edwin as the new Deiran king. Whilst Edwin had been an exile at Rædwald's court, he had had a dream where he was told that if he converted to Christianity, he would become greater than any that had ruled before him. Steven Plunkett relates that, according to the version of events as told in the Whitby "Life of St Gregory", it was Paulinus who visited Edwin and obtained his promise to convert to Christianity in return for regal power. After Edwin emerged as the ruler of Deira, with its centre at York, he became accepted as king of the northern Northumbrian province of Bernicia. Following his victory over the Northumbrians, Rædwald was not only king of the East Angles, but also the most powerful king amongst the rulers of the various English kingdoms, occupying the role which was later described by the term "Bretwalda". He is thought by many to have been buried in the sumptuous ship burial at Sutton Hoo.