She read art history at the University of Nottingham and began writing pieces for the TLS, The Burlington Magazine and art journals while still a post-graduate. She has a specialist interest in twentieth-century British art and first established her reputation with Roger Fry: Art and Life. She went on to write lives of the artists Vanessa Bell, John Minton, Duncan Grant, Gwen Raverat and John and Myfanwy Piper, as well as a biography of the poet Stevie Smith. Her survey history, British Art since 1900, in the Thames & Hudson World of Art series, has been widely used in schools, colleges and universities, and in the mid-1990s she was commissioned by Tate to write a centenary history of this national institution. Between 2000 and 2015, she taught at Newcastle University, becoming Professor of Art History. She acted as Editor of The Burlington Magazine, 2015-16, and is now is Emeritus Fellow of Clare Hall, Cambridge. She is also a Fellow of the Royal Society of Literature, an Honorary Fellow of the Royal College of Art and in 2005 was made a CBE for Services to Literature.