During the 1970s, Black Sabbath dominated Heavy Metal. In an age of bona fide super-groups they were unquestionably the heaviest thing on the planet, and remained a solid unit whilst others around them suffered ongoing membership fall-outs and line-up re-incarnations. Tony Iommi, Geezer Butler, Ozzy Osbourne and Bill Ward weathered internal storms but remained resolute, conquering the globe in the process, selling almost fifty million albums and delivering absolute, pure Heavy Metal. But in 1977 the unthinkable happened - Ozzy decamped. Over the next two decades a succession of vocalists and other musicians took up the challenge, perhaps most notably Ronnie James Dio and Ian Gillan, and Tony Iommi succeeded in breathing new life into Black Sabbath time and time again. Albums crafted in those times of adversity are now recognised as some of Sabbath's finest moments, and the huge array of players that travelled through the ranks is a constant source of fascination and rumour for Sabbath fanatics. Here for the very first time, and with exclusive interviews, is the definitive account of those years.