The Ruth Rendell Mysteries (1987) : 11x1

As a teenager, Guy Curran leads a street gang and for three years is the lover of Leonora, whose middle-class background is a world away from his own. Leonora's family disapprove of her boyfriend. As the years pass, they drift apart. Guy becomes a successful business man and Leonora goes to college and then gets her first job. When they meet again, Leonora says there is now someone else in her life, but Guy can't accept this. His obsession deepens and turns into a murderous madness...