Cormack has been a trustee of the Churches Preservation Trust since 1972, and is a Fellow of the Society of Antiquaries of London. He has been a council member of British Archaeology since 1979, and is also a Liveryman of the Worshipful Company of Glaziers and Painters of Glass for the same length of time. From 1983 to 1993, he was Trustee on the Winston Churchill Memorial Trust. He is a consultant and adviser to FIRST, an international affairs organisation since 1985. He is a Vice-President of the Royal Stuart Society and Patron of the Heritage Crafts Association.