Garrett was the quintessential teen idol. At 58, he has written a painful memoir about his fall from stardom, detailing “the darkest and worst things I have ever been through”. In the early 1970s, the handsome youngster appeared in dozens of films and television shows. When he moved into the world of pop music, he became a global superstar. Then his life collapsed, in a whirlwind of heroin addiction, car crashes, bankruptcy and jail.