Ozzy Osbourne's Black Sabbath bandmates had no idea he had relapsed.
The 65-year-old star confessed to breaking his sobriety by taking drugs and drinking again earlier this year and his fellow rockers Geezer Butler and Tony Iommi admit they were shocked to learn the extent of his downfall, especially as Ozzy had been spending time at Tony's house to record their latest album, '13'.
Tony, 65, said: "You know what, 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 [Ozzy's wife] Sharon [Osbourne] told me. I just couldn't believe he'd been drinking again. I didn't see any signs of it."
Geezer, 64, added: "He 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."
The duo admit Ozzy's behaviour changed very little while working on the record and Geezer even believes his work was "better than ever".
Speaking to Classic Rock magazine, he said: "It certainly didn't affect his performance in the studio ... to us, he'd worked better than ever. Sharon told me and Tony, and by that time Ozzy had gone into rehab."