Come back in time with me to 1981. Black Sabbath are playing at the Hammersmith Odeon, for the first time without Ozzy - widely regarded as the soul of the band - who has been sacked by guitarist Tony Iommi, but will soon become a superstar in America. The man attempting to take Ozzy's place is called Ronnie James Dio. He is very short, and the level of the billowing clouds of dry ice is set too high for him, so as he stretches his arms up to the roof, only his fingertips are visible. Someone starts to chant - "Ozzy! Ozzy!" - and soon the whole venue is joining in, so that you can hardly hear the music. Spinal Tap could never quite live up to the hilarious madness of heavy metal reality.
Having first experienced him as an absence, the sight of '95 vintage Osbourne should not come as a shock, but it does. You could probably fit three of his lean, wiry current selves into the bloated Oz-monster of yesteryear. "When I eventually put the bottle down," Ozzy explains cheerfully, "my addiction switched to exercise." Once aboard the hotel gym exercise bike, "the natural endorphins kick in and I could go on forever." In Japan recently, his new guitarist brought back some bootleg old-look videos. "I couldn't believe them," Ozzy shakes his head, "I looked like Elvis!"
In fact, he looked worse than Elvis; he looked like Larry Hagman in drag. At 46, Ozzy Osbourne now feels, and looks "fitter - both physically and mentally" than he did 20 years ago. He has a new album, excellently titled Ozzmosis. As he sips diet Cokes and nibbles at the odd strawberry, his wife and manager Sharon, and school- uniformed son Sam, sit in the hotel bedroom next door, watching True Lies on video. Without Sharon, Ozzy freely admits he would probably be "dead, or in prison". As it is, the only legacy of decades of alcoholism and drug dependency is a tendency to foam slightly at the mouth at moments of peak conversational intensity.
"What Sharon would do to try to stop me drinking," Ozzy remembers fondly, "was take my clothes. So if I wanted to get a drink I'd have to dress up in hers." This gambit shaped one of the defining moments in Osbourne lore - the events now known as the Alamo Incident. "I was alone in my hotel room in San Antonio and I wanted the hair of the dog, so I put one of her dresses on. I'm walking around the town with this green evening dress on, slurping from a bottle of Courvoisier, drunk as an idiot, and I want to take a piss, so I see this old wall and I think this'll do, but unfortunately it's the Alamo."
Charged not just with being drunk in public but also with the rather more serious offence of urinating on a shrine, it would be fair to say that Ozzy was not flavour of the month in Texas at this point. Soon afterwards he went into a coffee shop "full of normal, straight-laced people" with his bodyguard, a Vietnam veteran, and another terrible thing happened. "Someone in a suit and tie started screaming 'Put Jesus in front of you' and all the other people in the restaurant turned out to be with him, so they all joined in. Then this Rambo guy who's with me goes into kill mode and starts throwing them all through the window. I had to crawl out of there literally on my hands and knees."
Being widely viewed in the US as Satan's emissary certainly has its funny side, but the implication of Osbourne's song "Suicide Solution" in a number of teenage suicides was no laughing matter. At pains to explain that the song was about alcoholism rather than suicide - "It's 'solution' meaning a liquid" - Ozzy is understandably bewildered by the priorities of those who sought to drag him through the US courts over it. "I don't know about you," he says sadly, "but if I went home tonight and found my kid lying face down in the bath with a suicide note saying 'Goodbye Dad, I'm off' and a New Kids on the Block album was playing on his stereo, the last thing on my mind would be suing the group - I'd be grief-stricken."
It was the authentically sombre character of Black Sabbath's music - Osbourne's haunted bellow emerging from the dank grind of Iommi's guitar - that gave it such enduring power, but the dark trappings they dressed it in were pure showbiz. "When we came out of seeing The Exorcist we had to all stay in one room together," Ozzy laughs, "that's how black magic we were." They were messengers from Birmingham, not Beelzebub. Ozzy's mum and dad both worked in the motor industry, and his own last "proper" job before consigning himself to full-time rock 'n' roll dissolution was testing car horns.
Though his greatest success has been in America, the Osbourne family home is now in leafy Beaconsfield, Bucks. The man who once bit the head off a dove in a drunken bid for attention in a record company office, who had to be immobilised with rabies shots after doing the same thing to a dead bat when someone threw one at him on stage, is unlikely animal rights activist material, but Ozzy is very angry about conditions in quarantine. "People talk about cruelty to animals, but you want to go down there man, it's sick. And it's a thousand quid a month for six months." Ozzy had a Yorkshire terrier in there once that ran away as soon as it got home: "I thought, 'bye bye six grand'."
With his first album in four years, Ozzy is emerging from a sort of quarantine himself. The desire to drink has "totally gone" now - "I never liked the taste anyway" - so how was this miraculous cure effected? Osbourne went to a few Alcoholics Anonymous meetings but "didn't feel very comfortable" with them. "If you've had one of your limbs amputated," he explains, "you don't want to sit in a room with a lot of one-legged men talking about it." At the bottom of his own drink problem seems to have been an almost pathological insecurity.
"If I didn't wake up in the morning worrying," he explains, "I'd worry because I didn't have a worry, then it would escalate into this great monster sitting on my shoulder." An addiction therapist put him on Prozac - "You still get the feelings of insecurity, but it sort of nips them in the bud" - and this, together with the odd dash of Valium and a healthy measure of newfound self-awareness, saw him through.
His words are punctuated by the jangle of enough gold jewellery to make the most hardened Old School rapper jealous. As so often with Osbourne - saying of the day: "I don't to be anyone that I'm not, I'm just a working class hero" - his starry trappings have an earthly explanation. The rings and chains are "guilty gifts" from Sharon. "When she does some damage on the credit card, I always get a bangle," Ozzy grins. I compliment him on a particularly fine gold finger-protector which looks like a fleeing caterpillar with a diamond cross in its back. "Here," he says, offering it across the table, "try it on, it's cool." Funnily enough, he is not wrong.
8 'Ozzmosis' (Epic, CD/Tape) is out on Monday. Ozzy Osbourne tours in November.