Adrian Keith Graham Hill was born in Charlton, London and educated at Dulwich College. He studied art at the St John’s Wood School of Art and at the Royal College of Art. During World War I he joined the Scouting and Sniping Section of the Honourable Artillery Company but by 1917 he was appointed an official war artist and many of his paintings and sketches of the Western Front are now in the collection of the Imperial War Museum. After the war, he took up painting professionally and also taught at Hornsey School of Art and Westminster School of Art. His work combined elements of impressionism and surrealism as well as more conventional representations. He exhibited at the Royal Academy, New English Art Club, Royal Society of British Artists, Paris Salon and elsewhere.
In 1938, while convalescing from tuberculosis at the King Edward VII sanatorium in Midhurst, he passed his time by drawing nearby objects from his hospital bed, and found the process helpful in aiding his own recovery. In the following year occupational therapy was introduced into the sanatorium and he was invited back to teach drawing and painting to the other patients, many being the first injured soldiers returning from the war. Hill found that the practice of art not only helped take the patients' mind off their illnesses or injuries but also helped to release their mental distress by expressing their anxieties and the scenes they had witnessed during the war. In 1942 Hill first used the term Art Therapy and in 1945 published his ideas in the book Art Versus Illness. He later became president of the British Association of Art Therapists.
He wrote many books on painting theory and techniques, including On Drawing and Painting Trees (1936) and The Pleasures of Painting (1952). In the 1950s and 1960s he presented a BBC children’s television series called Sketch Club. He lived near Midhurst, Sussex.