British art historian and administrator, son-in-law of Barbara Hepworth and Ben Nicholson. He studied modern languages at Cambridge University and history of art at the Courtauld Institute, London. After working for the Arts Council, he taught at the Courtauld Institute, 1957–79, then was director of the Tate Gallery, 1980–88, a period that saw the opening of Tate Liverpool and the inauguration of the Turner Prize. In addition he served on numerous committees, including that of the Contemporary Art Society. His writings, all on late 19th-century or 20th-century art, include two highly regarded introductory surveys—Modern Sculpture (1965) and Modern European Art (1972)—as well as numerous more specialist studies, notably on Hepworth and Moore. He has also organized and catalogued several major exhibitions.