"Speak up, we can't hear you... we're leaving." Pity good' ol Bob Newhart, veteran stand-up comic from Chicago. He'll have been performing live for 40 years come March 2000, and, Bob, I have to say those jokes about driving instructors and Nutty Walt Raleigh on the phone with news of tobacco don't get any younger. Nor do your audiences, to judge from the hard-of-hearing crowd on Sunday night.

The row behind me discussed business meetings. They asked one another to repeat punchlines. They barked "Who's he?" when Neil Innes, one-time Bonzo Dog, gurned through a warm and funny singalong warm-up act. They didn't laugh much.

Between the pops and crackles of a sound system that Innes described as "sizzling bacon", Newhart looped us back to a world of jokes which felt like the verbal equivalent of the wry New Yorker cartoons, circa 1964. That was the year he last performed in London. "You've obviously been keen to have me back," he said, which raised half a laugh. And here's the trouble with Newhart's off-the-cuff humour. It can be as dry as a martini, immaculately timed, yet missable to an audience that, all too often, needed signs saying "Joke! You may laugh now". Or not. The other trouble is that before telling politically incorrect jokes, an unsure Newhart made sure we knew he was a quarter German and three-quarters Irish. It really shouldn't matter, Bob. I know Americans don't tell too many un-PC jokes in 1999, but they're usually some of the funniest, even if yours don't necessarily translate well into English: "How does an LA family know its home's been broken into by a Vietnamese gang? Simple. The dog's gone and someone's completed the math homework."

I can tell this hasn't made you laugh. Newhart was on safe ground with the old gags he recorded on disc donkey's years ago, and which he tells as if making them up on the spot. He should have appeared at the Comedy Store, dropped his inhibitions and showed a younger generation - who would have heard him loud and clear - just what a very funny man he really is.