Hayes was born in London, and studied at Christ Church, Oxford and the Ruskin School of Drawing. He was on the staff of the Royal College of Art and was one of the most significant art teachers of his generation, nurturing such talents as David Hockney, Peter Blake, RB Kitaj and Patrick Caulfield. He was elected a Royal Academician in 1963 and was a regular exhibitor at the Summer Exhibitions. Hayes also wrote widely on art history, a discipline he considered essential for any artist; and published a series of books on painters, including Renoir, Rembrandt and Stanley Spencer.