Robert Plant is a living legend. The front man of Led Zeppelin, one of the biggest and most influential rock bands of all time, Plant defined the very notion of what it means to be a rock god. The sheer scale of Led Zeppelin's success is extraordinary. In the United States alone they have sold seventy million records, a figure surpassed only by the Beatles, while "Stairway to Heaven," the band's most famous song, has been played more times on American...