Bede was a Northumbrian, and this tinged his work with a local bias. The sources to which he had access gave him less information about the west of England than for other areas. He says relatively little about the achievements of Mercia and Wessex, omitting, for example, any mention of Boniface, a West Saxon missionary to the continent of some renown and of whom Bede had almost certainly heard, though Bede does discuss Northumbrian missionaries to the continent. He also is parsimonious in his praise for Aldhelm, a West Saxon who had done much to convert the native Britons to the Roman form of Christianity. He lists seven kings of the Anglo-Saxons whom he regards as having held "imperium", or overlordship; only one king of Wessex, Ceawlin, is listed, and none from Mercia, though elsewhere he acknowledges the secular power several of the Mercians held. Historian Robin Fleming states that he was so hostile to Mercia because Northumbria had been diminished by Mercian power that he consulted no Mercian informants and included no stories about its saints.