Duncan has over 30 years of experience in the heritage sector; for Historic England, English Heritage and local authorities. He studied planning and building conservation at Newcastle and York Universities. Duncan has held senior strategic roles in Historic England (formerly English Heritage) since 2005. He establishes its position on a wide range of strategic environmental, cultural and planning issues and is responsible for national listing work. He is a Fellow of the RTPI and also of the Society of Antiquaries of London and a member of the Institute of Historic Building Conservation. He is a Trustee of The Society for the Protection of Ancient Buildings.