Welcome to the deranged world of The League of Gentlemen, a bizarre cross between Monty Python and the Theatre of Cruelty. Like a Victorian fairground freak-show, the twisted trio of Mark Gatiss, Steve Pemberton and Reece Shearsmith specialise in grotesques. It is a universe peopled by types not usually at the top of the list of comedy topics: deformed paedophiles, transsexual magicians and grieving mothers. Many sketches in their show at the Canal Cafe cause you to shift uneasily in your seat, as you wonder to yourself, "Is this really an appropriate subject for humour?" There is no shiny-happy, Little and Large-style cosiness about the material; they all obviously swallowed whole the writings of the Marquis de Sade at a very early age.
It is this darkness visible that gives The League a distinctive edge and led to a ferocious bidding-war between agents and commissioning editors at the Edinburgh Festival last year. In one sketch barely on nodding-terms with conventional comedy, a guide showing tourists around a cave suddenly lurches from listing the celebrities who have been there before - "Don Henderson of Bullman fame and the Chuckle Brothers, you may have seen their autographs at the ticket-booth" - to revealing a past disaster at the site to which he contributed: "I now prefer to sleep with the light on because it's in the darkness that I see the boy's face - eyes protruding, tongue out, black."
The best sketches remind us that comedy is as much about sadness as silliness. One routine - which I'm trying desperately to resist calling "Pinteresque" - centres on a boyfriend visiting his girlfriend's parents for the first time. Their initial civility evaporates as the parents descend into an undignified slanging-match. "Don't end up like us, you're still young," the father urges the boyfriend, before adding wistfully: "Where did the years go to?"
Excellent performers, the dinner-jacket-wearing threesome can capture characters at the drop of a wig. Using only a ginger mop-top, a leopardskin scarf and an artfully placed piece of Sellotape under his nose, for instance, Pemberton is transformed before our very eyes into the predatory, child- molesting German exchange teacher, Herr Lipp.
There was a banned video nasty in the early 1980s called Nightmares of a Damaged Brain. The League of Gentlemen must have used it as the inspiration for a deft, dark show. Laugh? I nearly slit my wrists.
The League of Gentlemen continue every Monday at the Canal Cafe Theatre, London, W2 (0171-289 6054). To 9 June James Rampton