You can never be sure quite how good a comic is until you see them in the flesh - Robin Williams, it turns out, can be a very good comic indeed. Playing his first full London show for 25 years last night, the stand-up and actor began his act with an energy that welcomed a 900-seat auditorium into the palm of his hand.

Now, sure, Mork & Mindy and three decades of films have taught us that Williams is a firecracker - and we also know how “manically inventive” can veer into “irritating”, even before it's turned the bend into suffocating schmaltz. But as he zoomed into material about the London Olympics, the well monikered Tessa Jowell - “like Agnes Moorehead, sometimes the name just fits” - and Ken Livingstone's legacy on London traffic, his charisma was unquenchable. Those £125 stalls tickets - proceeds to the Prince's Trust - were looking like a good deal.

But Williams couldn't quite keep up that level of connection over the rest of a skilful, superfluent set. He mixed some surprisingly familiar stand-up tropes - the woes of putting on a condom, the lunacy of mobile phones - with a lot of American references designed for his earlier US tour. Sure, if he did a Bush gag, it might well be a good one: “W comes from a family where the smart brother is called Jeb.” And though I found some of the racial stereotypes - an Indian call-centre worker, a Southern hick - a bit weak, he performed the hell out of it all. After 90 minutes he left to a hero's ovation.

Yet there was something detached about the show. Only after about an hour did he really break away from the everyman observations of the television watcher, the man in Starbucks. “I started drinking again after 20 years,” he told us. “I went to rehab in wine country just to keep my options open.”

You didn't have to be a celebrity-watching ghoul to want him to go even farther than the sharp but short routine about alcoholism that followed. He talked about the fallacy of calling yourself “a functioning alcoholic”, then about Viagra, porn, divorce - but it was swift, delivered in the second person, junked too soon to let us feel were were really connecting with him.

Contrary to his image as a guy who wildly improvises on stage, he kept fairly tightly to his set. He only really recovered the incredible intimacy of his warm-up in some routines towards the end - what idiot designed our genitalia? How do cats torment dogs? - that showed up the lack of imaginative flourishes elsewhere. What we got was a well-crafted, gag-heavy stand-up show. A propulsive, multi-faceted performance that just needed a bit more Robin Williams in it.

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