In 1988 Máire Herbert's magisterial Iona, Kells and Derry laid out a clear map of the progression of the authority within the Columban familia along the lines indicated in the title, with the comarbus or ‘successorship’ of the founder saint Columba passing to each of the named major monasteries within the federation from the sixth to the twelfth century. Importantly, she gave careful consideration to the nature of the ‘hand-over’ periods between the institutions, making it clear, for instance, that despite the construction of the monastery of Kells during the period 807–14, the idea of Iona's abandonment for Kells in the early ninth century owing to Viking raids was simply a modern myth. The comarbus of Colum Cille, by her reckoning, arrived in Kells de facto only with the accession of the comarba Pátraic, Mael Brigte mac Tornáin (891–927). There is no clear evidence that Mael Brigte was based at Kells itself, but his long rule (nearly forty years in Armagh, thirty-six as successor of Colum Cille), apparently spent in Ireland, and the certain fact that by the early eleventh century successors of Columba were based there, made it probable to Herbert that subsequent tenthcentury successors were in Kells de jure. Its loss of authority came only in the twelfth century, with the rise of Derry under the patronage of the Mac Lochlainn dynasty, 1150 being, in John Bannerman's words, Derry's ‘annus mirabilis’.