“This island, stiff-necked and stubborn-minded, from the time of its being first inhabited, ungratefully rebels, sometimes against God, sometimes against her own citizens, and frequently, also, against foreign kings and their subjects.”
Saint Gildas describing his fellow Britons.
What you notice about the Celtic peoples is that the dynamic of political competition among them failed (in three of four cases) to generate a durable supralocal political authority.