Scandinavian kings in the British Isles, Oxford university press, Oxford, 1977, (ISBN0-19-821865-6)
Warlords and holy men: Scotland AD 80-1000, Édimbourg, Edward Arnold (Publishers) Ltd, 1984, (ISBN0-7131-6305-4)
Scandinavian York and Dublin: the history and archaeology of two related Viking kingdoms, Irish academic press, Dublin, 1987, (ISBN0-7165-2365-5)
A biographical dictionary of dark age Britain: England, Scotland and Wales c. 500- c. 1050, En collaboration avec Ann Williams, Seaby, Londres, 1991, (ISBN1-85264-047-2)
King Alfred the Great, Oxford university press, Oxford, 1995, (ISBN0-19-822989-5)
Medieval Europeans: studies in ethnic identity and national perspectives in Medieval Europe, MacMillan, Londres, 1998, (ISBN0-333-67219-4)
Seanchas: studies in early and medieval Irish archaeology, history and literature in honour of Francis J. Byrne, Four Courts press, Dublin, 2000, (ISBN1-85182-489-8)