At some point Ceawlin ceased to hold the title of "bretwalda", perhaps after a battle at Stoke Lyne, in Oxfordshire, which the "Chronicle" dates to 584, some eight years before he was deposed in 592 (again using the "Chronicle's" unreliable dating). Æthelberht certainly was a dominant ruler by 601, when Gregory the Great wrote to him: Gregory urges Æthelberht to spread Christianity among those kings and peoples subject to him, implying some level of overlordship. If the battle of Wibbandun was fought c. 590, as has been suggested, then Æthelberht must have gained his position as overlord at some time in the 590s. This dating for Wibbandun is slightly inconsistent with the proposed dates of 581–588 for Ceawlin's reign, but those dates are not thought to be precise, merely the most plausible given the available data.