 While several kingdoms in Britain — East Anglia, Fortriu, Mercia, and Northumbria — would collapse under the shock of Viking attacks, their impact in Ireland was very much less immediate.In the first half of the ninth century, raiders appear to have come in small groups, increasing in size until larger forces appear, such as that led by the shadowy Turgéis (Turgesius) in the 840s, and those led by Amlaíb and Ímar from the 850s onwards.Vikings would be both enemies and allies for Cerball and other Irish kings.