But now, at the exact appointed hour, there he was, skipping into the applause without ceremony and indeed without a shirt. These days the Ig sports a torso that would not look out of place at the World Athletics Championship, its taut muscularity honed over 25 years of selfless abuse. All the evidence of his former life appears to have accumulated on his face, which, in its colour and contours, has more than a passing resemblance to Keats's death-mask.
Though he now favours aerobics and vegetarianism over uppers and downers, anyone who feared that, at the same age as John Major when he became Chancellor, the Ig had grown up and toned down would have been immediately relieved. He bounced across the stage, whirling his arms around their double-jointed shoulders, mouthing a river of obscenities, flagellating himself with an electric cord, throwing his mike-stand about without care for where it landed, attacking his audience for throwing plastic cups at him ('Is that all you can manage? You're pathetic. Go on, throw something that hurts.')
His hair, which has enjoyed scant acquaintance with shampoo, flailed around like a dervish's head-dress. It was an electrifying, athletic performance, which, unlike Linford Christie's, was not spent after 10 seconds: the Ig kept going like this for 90 minutes.
Behind him three hairy musicians provided a wall of 4/4 thump, which - though Iggy students might have been able to pick out 'Real Wild Child' and 'The Passenger' (with its mind-stretching 'Na-na-na-na-na-na-na' chorus) - cheerfully merged into one.
The Ig did try to differentiate, explaining the provenance of many of the songs: 'This one's about TV. If you're on TV, you're like a god. And if you're not on TV, our society says, who the hell are you?' Which is basically U2's message, but without recourse to miles of cabling.
Most of the evening, however, was driven by less sophisticated observation. 'This is a song about the emotion called hate,' he said at one point. 'How you feed it and keep it going. It's called 'Hate'.'
And off it went, very loud, very fast and very angry, the Ig strapping himself into a Gibson guitar which he proceeded to torture in a manner that should have alerted Amnesty International. The source of his anger may be uncertain, but Iggy is quite democratic in spreading it around. At various points in the evening he abused those members of the audience gathered on the stairs, those in the balcony and, that old rockers' stand-by, the bouncers.
This last was a touch unfair. If the Ig was energetic, the busiest men in the Forum were the burly security guards, who had a steady stream of boarders to repel from the stage. Every 30 seconds or so someone would climb on to the shoulders of the sweating, pogoing pack, lie back and allow himself to be passed stagewards, at which point the bouncers, out-numbered 50 to one, would shove him back.
The Ig, spotting all this, felt left out, took a run past the footlights and dived into the scrum himself, to grab a piece of this audience surfing. As he was passed across the heads of worshippers, their hands becoming increasingly intrusive, the bouncers struggled to grab him, hauling him back for his own protection, like the parents of a hyperactive child.
'Let me do it, you suckers,' he said, as he reclaimed his microphone. Except he didn't say 'suckers'.
Then, as if to reinforce his anger, he swaggered to the front of the stage, fished about in his flies and hauled out the Pop appendage, flashing it around in the enthusiastic faces of the front row. In truth it was not as substantial as legend has it; maybe it was cold up on stage.
After this revelation, he decided that trousers were as unnecessary as a shirt, unfastened his waistband and spent most of the rest of a splendid and furious concert with them gathered around his ankles, hopping around with all the threat and rebellion of a three-year-old fresh from the potty.
It was at this point that the real reformation in Iggy Pop's character became clear: these days he wears underpants.