Miles was married twice to the British playwright Robert Bolt, 1967–1975 and 1988–1995. He wrote and directed the film "Lady Caroline Lamb", in which Miles played the eponymous heroine, and wrote "Ryan's Daughter", as well. After his stroke, the couple reunited and Miles cared for him. "I would be dead without her", Bolt said in 1987, "When she's away, my life takes a nosedive. When she returns, my life soars." The couple had a son, Tom, who is now a watch dealer.