Ozzy Osbourne, Tony Iomi and Geezer Butler of Black Sabbath attend the Classic Rock Roll of Honour at The Roundhouse on November 14, 2013 in London, England.
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Ozzy Osbourne's bandmates in Black Sabbath had no idea he'd fallen off the wagon while making 13.

Osbourne revealed his sobriety issues earlier this year when the Sabbath reunion album was released. Now Tony Iommi tells Classic Rock magazine, "I couldn't believe it. He was working at my house and I didn't pick up on it at all. None of us did. He really hid that well! It was a shock, actually, when Sharon [Osbourne] told me. I just couldn't believe he'd been drinking again. I didn't see any signs of it."

Geezer Butler adds, "[Ozzy] was really good at keeping it secret. I thought he was talking a lot -- he used to drive us nuts because he wouldn't stop talking -- but we put that down to the excitement of doing the album. Anytime I'd had a drink, he'd be saying, 'Oh, have you got a hangover?' And meanwhile he was doing all kinds of stuff. But it certainly didn't affect his performance in the studio -- to us, he'd worked better than ever."