John McCann was a professional architectural photographer for 25 years, photographing modern buildings for architects, architectural journals and public bodies. In middle life he became more interested in vernacular architecture, the study of minor historic buildings - farmhouses, cottages, barns, granaries, dovecotes, etc

As a mature student he took an Honours degree in history at King’s College, University of London, in 1980.

He is a former Inspector of Historic Buildings for Essex County Council and English Heritage, in which capacity he examined and Listed about two thousand historic buildings in Essex.