 The circumstances of their arrival are unknown, and theories include categorising them as "raiders", as "invaders" who established a hegemony, and as "foederati" invited by the Romans.It might as easily have been the consequence of a depopulation in Wales caused by plague or famine, both of which were usually ignored by ancient chroniclers.What is known is that their characteristically Irish circular huts are found where they settled; that the inscription stones found in Wales, whether in Latin or ogham or both, are characteristically Irish; that when both Latin and ogham are present on a stone, the name in the Latin text is given in Brittonic form while the same name is given in Irish form in ogham; and that medieval Welsh royal genealogies include Irish-named ancestors who also appear in the native Irish narrative "The Expulsion of the Déisi".