In 1994 David completed his Research Degree (Ph.D) on "Design Effectiveness for People with Severe Disabilities". This, as well as his personal knowledge of disability, has made David a leading figure on the subject. He has worked on a wide range of projects including the Roundhouse in Camden, Tate Britain, Royal Festival Hall, King's Cross Station, Ashmolean Egypt Galleries, Sir John Soanes Museum, Sadler's Wells Dancehouse.