Ozzy Osbourne's Black Sabbath bandmates have revealed they were "shocked" that he had relapsed.
Tony told Classic Rock Magazine: "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 told me. I just couldn't believe he'd been drinking again. I didn't see any signs of it."
Geezer 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."
Ozzy revealed that he relapsed and had fallen off the wagon in a statement on his Facebook page in April.
He wrote: "For the last year and a half I have been drinking and taking drugs. I was in a very dark place and was an a**hole to the people I love most, my family. However, I am happy to say that I am now 44 days sober."
The pair said they didn't notice any signs because Ozzy didn't seem troubled during the album's recording process.
Geezer 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."