Dr Wiliam worked as Assistant Keeper, Director and Deputy-Director at Amgueddfa Cymru-National Museum of Wales, and is an authority on the vernacular buildings of Wales. He has published extensively on the subject, and was responsible for the addition of many such buildings to the Museum’s collection at St. Fagans. Appointed Chairman of RCAHMW, retiring in 2016, he is also Chairman of the Nantgarw Chinaworks Trust.