Ricky Gervais, Wembley Arena

Do look away now if you’re squeamish. Why? Because before the star turn has even made his entrance, a film is shown on the screen suspended above the stage. An earnest American advises that there is a global shortage. Jumbo jets have been spraying deliveries from the skies. Donations are coming in, but billions of gallons are simply not enough. He is drinking more than the world can supply. But what can this precious nectar possibly be?

Cut to a shot of a famous face vomiting milky white gloop into a toilet bowl, then wiping a few sticky deposits off his goatee. Ricky Gervais, ladies and gentlemen, is appealing for sperm donors. He simply can't get enough.

It's quite a daring way of saying hello, good evening and welcome. But entirely in character. The joke with Gervais is a simple one. How much can he risk offending his people without sacrificing their adoration? How many jokes about fatties and homosexuals and people with Down’s syndrome, about Muslims and paedophilia can flow from inside that head and out into the cavern of Wembley Arena, before he finally loses his audience, possibly for good?

He flirted with the possibility earlier this year when presenting the Golden Globes. He’ll no doubt have another go at offending America when this live tour gets there next month. But in his own parish, with his own flock gazing up at him, the co-creator of The Office can do very little wrong.

The show is called Science without ever doing much to earn the title. Yes, there’s a nod to chemistry in the stage set, got up to look like a mad genius’s lab. But as Gervais kept saying, “It’s not really about science.” Science for Gervais is probably not so much about being a fan on Stephen Hawking’s Facebook page. It’s more of a playground insult he shouts at the enemy, the V sign he continues to flick at the fictitious deity he previously featured in The Invention of Lying.

Disproving the existence of God is the closest Gervais gets to a moral or intellectual position. In truth he is rather more focused on proving his own omnipotence. It’s a sort of alternative theology of his. There may be no one up there with a long white beard, like there is in the Noah storybook he quoted in a routine that went on too long. But there is a short, fattish, middle-aged man with a medium-sized endowment who says “termites” and “girls” with a loamy Berkshire accent. He is his own church, in short, defined and underpinned by the achievements he trumpets, the awards and private air travel and immunity to the global downturn. “Just being honest,” he shrugged last night.

And then of course there are his detractors. These demonic figures from the press are fundamental to the Gervaisian belief system. Every time he pushed another envelope, broke another taboo, he mimed them onstage, tapping at their keyboards and telling him what he cannot say. “Ban him from the telly,” they suggest. “Good luck,” he retorts. It’s all one big act, of course, just like Dave Brent was. Either that, or Gervais is toxically insecure.

All of this went down exceptionally well. Gervais has managed to carve out a niche, which didn’t previously exist, for a comic who says the most appalling things and hears nothing but waves of laughter rolling back towards him from thousands of perfectly decent acolytes. He is at an exact polarity with Michael McIntyre, the only British comedian with the same level of box-office gigawattage. Where McIntyre says the things no one else bothers to, Gervais says the things no one else dares to. That can be the only reason why he’s not clapped in irons: he is a safety valve, an outlet who gives a voice to the ugliness in all of our souls so that we don't have to. He utters out loud what the march of civic evolution and social progress – it’s nothing so superficial as political correctness - has mostly silenced in the rest of us: selfishness, arrogance, spite, cruelty, the ability to refer to other people as “fucking maggots”. “I didn’t kill her in the end,” he said in one throwaway narrative, and then after a beat: “I just raped her.” The whole room erupted in shocked delight, and then he went back for even more: “Luckily she has Alzheimers.”

Not that Gervais can’t be as squeamish as the rest of us. He visibly shuddered at the memory of a Ken Dodd gig at Regent’s Park Open Air Theatre where a very large woman in the front pleasured herself to completion. But there’s no getting away from the fact that he’s at his funniest and most mercurial when least expected, when the wit is not about shock. There was a lovely little routine about Oscar Wilde's eagerness to declare his genius (it takes one to know one). It was fun seeing the creator of the famous dance give free rein to his underused physicality. A riff about the anger of spiders, or an orgiastic version of plate-spinning were hilarious. Maybe he should spare his audience the lectures about what is and isn’t funny. It's just not funny.