Ken Campbell's History Of Comedy Part One: Ventriloquism

National Theatre, London

Lamb Chop is dead - long live Lamb Chop! Can there have been more gladsome tidings this year than the news that the daughter of the late Shari Lewis has decided to revive the fortunes of the nation's favourite old sock? For those of you who haven't a clue what I'm on about, you're clearly too deprived or just too young to remember the American TV star who charmed millions by talking without moving her lips to a little embroidered friend. What's more, Shari was a woman, which in the peculiarly male - or just downright peculiar - bastion of ventriloquism is something of a first.

Lamb Chop is dead - long live Lamb Chop! Can there have been more gladsome tidings this year than the news that the daughter of the late Shari Lewis has decided to revive the fortunes of the nation's favourite old sock? For those of you who haven't a clue what I'm on about, you're clearly too deprived or just too young to remember the American TV star who charmed millions by talking without moving her lips to a little embroidered friend. What's more, Shari was a woman, which in the peculiarly male - or just downright peculiar - bastion of ventriloquism is something of a first.

Speaking of firsts, Ken Cambell's latest theatrical outing is the first in a series on the history of comedy. And where better to begin than with the profoundly strange art of ventriloquism which, as our Ken gleefully informs us, dates back 4,500 years to strange linguistic goings-on amid the Pygmies. Despite having paid close attention to his larky disquisition on glossalalia of the Languedoc (the gift of tongues), and gastromancy (the suspicious-to-the-point-of-being-fanciful business of swallowing spirits), I am, I'm afraid, quite unable to report back coherently on Cambell's line of argument. Where's an overhead projector when you need one? But then chronology or, indeed, any kind of logic, is the very last thing on Campbell's mind.

While this absurdly perambulatory lecture/demonstration - and the set - is littered with ventriloquist's paraphernalia (including knee-pals, which is insider-talk for what you and I think of as dummies), the whole deal is little more than an elaborate excuse for this engaging lunatic - sorry, theatrical one-off - to embark on his usual journey of a wildly linguistic ramble through autobiography, storytelling and shaggy dog stories. So much so that this time he has three real-life, tail-wagging dogs with him. Don't ask.

Daft as it may seem, you could argue that Cambell's patron saint is EM Forster of "only connect" fame. Few others would stand up in front of a paying audience to seduce them with outlandishly eclectic tales of everything from the Gospel applications of balloon-modelling to Gertrude Stein via the secret language of the Hainault First Sea Scout troupe and, mystifyingly, manage to tie them together.

The trouble is, he's so busy developing the art of the sidetrack that he sometimes loses focus. He's off loping enthusiastically down yet another new line of thought about Inuit sniffers or the rites of passage into manhood, but latterly you find yourself drifting away from the material for minutes at a time. Absurdity slides into whimsy that simply isn't strong enough to sustain attention. Then, just when you're about to give up the ghost, he suddenly reels you back in.

Go on, admit it: when was the last time you went to the theatre and spent a delirious few minutes attempting the Beecher's Brook of ventriloqual derring-do: "Who dared to put wet fruitbat turd in our dead mummy's bed? Was that you, Verity?"

To 9 Sept (020-7452 3000)