A wide-eyed girl at the back is popping some Fantasy, while a dude in a manky greatcoat pulls forlornly on a green pepper. There's a hippy clinging to his seat as the high from a Jack-in-the-Box ("It'll take your lid off") threatens to propel him from the room. And the happy soul talking to himself in the corner is doing his best to blow his brains on a reckless cocktail of cider, "grog" and Jaguar lager.

It could be the fall-out from a particularly seedy student party. But it is, in fact, a show called The A-Z of Drugs, playing at the London Comedy Festival last week. The creators of this anarchic narc-fest are James Poulter and Graham Duff, and theirs is a notable achievement - to have extracted mileage from one of the most hackneyed subjects in comedy: drugs.

If you had a gram of coke (or, in Poulter-&-Duff speak, Bolivian Shopping Powder) for every tiresome ganja gag on the circuit, you would be a very rich drugs baron indeed. But by cataloguing the highs and lows of narcotics abuse in a pseudo-educational manner, as opposed to the knowing, self- congratulatory, out-of-it-man references of most comedians, Poulter & Duff distance themselves from their topic, while keeping their stash of drug humour as fresh as a newly plucked mushroom.

This approach worked wonderfully for Pete McCarthy in his Hangover Show, but Poulter & Duff have taken the idea a stage further by inviting audience participation. And there's none more gullible than a comedy crowd up for free "drugs". Hence Jeff, the unfortunate punter sucking the "cerobonin" (should that read "cerebrum") out of a pepper: it's a show as much about audience as substance abuse.

Some items will strike a chord with any ingenue who's ever been duped on a street corner in a dodgy part of town into buying a quarter of tea leaves or a lump of liquorice. Duff, drawing frantically on a lit banana, details the hit: "It's a feeling of ordinariness, of similarity, of nothing being any different."

Their "research" has also produced the occasional medical breakthrough: until Poulter & Duff came along, science was unaware that the urine of reindeers fed on magic mushrooms produces a mild hallucinogenic effect on the drinker. Watch out for "Liquid Rudolph" or "Santa Fanta" at this year's Chrismas parties.

The festival, essentially a hangover for Londoners who couldn't be doing with Edinburgh, also aired another double-act of the future, Henrietta Garden and Phillipa Fordham. One of the few festival shows to sell out, with their fetchingly titled Girls with Big Jests, the duo served up the best pair of bitching gossips since Les Dawson last leant over his garden fence for a chinwag and a cuppa.

Tea was one of the milder stimulants at Poulter & Duff's show, but then heaven knows what they'd used as a sweetener. The Brighton-based double- act are dangerous men with time on their hands. And their next project? The A-Z of Taboos, featuring the Queen Mother and a clenched fist. That'll be some royal command performance.