He graduated in history from the former University College, Cardiff, in 1975, and pursued a career in secondary school teaching in Mountain Ash, South Wales till 1983.
While serving as a schoolteacher he completed a doctorate on the Anglo-Norman twin aristocrats, Waleran of Meulan and Robert of Leicester, subsequently published by Cambridge University Press.
[3] From 2013, he held a Leverhulme Trust Major Research Fellowship and in 2015 he was a member of the Institute for Advanced Study, Princeton.
[4] Since retirement he has devoted his energies to the ongoing Victoria Counties of England series on Yorkshire East Riding, publishing a two volume study of Howdenshire wapentake and the reconstruction of a medieval Howdenshire gentry cartulary, constructing an edition from 17th-century antiquaries transcripts.
He was a member of the academic team which edited and translated into English the contemporary medieval biography of Marshal[7] His books on the aristocracy of England and France in the High Middle Ages, have been characterised by his incorporation of English social history into the mainstream of continental scholarship.