THE LAST time Billy Connolly set up camp at the Hammersmith Apollo, in May 1994, he was bizarrely clean-shaven. He looked like a tawny owl with a grudge. Whatever might or might not have happened to the ebullient Glaswegian's comedic powers since then, no one can doubt his talent for facial hair. A striking new beard in forbidding Old Testament silver- grey now adds further gravitas to his already imposing countenance.

Sheer force of personality enables Connolly to carry off material that would embarrass many a lesser comic. His John-Major-as-Clinton-style- sexual-oppressor routine, for example, might have been rescued from the very bottom of Rory Bremner's wastepaper bin; but Billy keeps on banging away at it until, strangely, it becomes almost hilarious. Some have sought to use the harrying, aggressive quality which has long been a part of Connolly's stage demeanour as an excuse to write him off as an overgrown playground bully. But to do this is to miss the copse for the bushes.

As with many other great performers (Johnny Rotten, Snoop Doggy Dogg and Hattie Jacques spring to mind) the key to Connolly's enduring appeal is not so much a gap between what he says and the way that he says it. It's the fact that the apparent congruity between his message and its delivery does not quite ring true. When he tells an extended and not particularly amusing story about a chance meeting, years later, with "Isobel", the voracious female responsible for his sexual initiation on a graveyard slab, it ought to seem vain and graceless, but somehow it doesn't. Even amid the glossiest paintwork of Connolly's self-belief, there are always intriguing drip-marks of insecurity.

At his best - describing underwear hanging on a line, the genital imprint disconcertingly visible, like some reproductive Turin shroud - Connolly has a painter's eye for visual detail. But it is to a preacher that he is most often compared, and as often happens with lapsed believers, the vehemence of his disillusionment can take the breath away as readily as the most intense religious profession. "St Christopher is not a saint any more," he observes bitterly. "I don't know what he did, but the child on his shoulder was a bit of a giveaway."

At moments like this you can't help but wonder how Connolly's rage has stayed so fresh throughout so many years of acclaim and plenty. It's hard to avoid the suspicion that some of it must be inwardly directed. Not since Marilyn Monroe has anyone been so obsessed with their roots: hence, perhaps, his compulsion to keep hitting Scottish photographers ("It felt good, I felt cleansed: It was like having a shower") - he doesn't like the thought of what they might be seeing through their viewfinders.

The real irony of all this is that the paying public could not care less about it. When Connolly makes his third or fourth implicitly self-flagellatory reference to what an overpaid scum-sucking Hollywood sell-out he is, the audience smile indulgently, as if to say: "We know you are extravagantly rich Billy, and you deserve to be, so get over it."

Billy Connolly: Apollo, W6 (0990 405040), to 8 Feb (returns only).