Leonard was born in Bangalore, India. He studied design and illustration at St Martin's School of Art, London from 1954 to 57. In the 1970s he took up painting, having worked as an illustrator throughout the previous decade. A figurative artist, Leonard is particularly known for his nudes, which combine photorealistic intensity with abstract qualities of design. He is also a successful and popular portrait painter; he was commissioned by the Reader's Digest magazine to paint Queen Elizabeth II in celebration of her sixtieth birthday (National Portrait Gallery, London).