After 15 years in practice in central London, he was appointed Deputy Secretary of the Royal Fine Art Commission (RFAC), and then Director of CABE's design review programme. In 2005 he founded Peter Stewart Consultancy. Major projects on which he has provided advice on architecture, urban design and the historic environment include the Chelsea Barracks project in Westminster and the Shell Centre project in Waterloo; the latter is one of many projects for which he has provided expert evidence at public inquiry. He has served as a member of the London Advisory Committee of English Heritage, as chair of the East Midlands regional design review panel, and as a member of a number of other design review panels.