Sketch shows: All aboard the comedy train

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Ten years ago, Emma Thompson wrote and starred in her own sketch show. At the time, a couple of chums of hers from the Cambridge Footlights were doing a roaring trade hawking traditional skits in A Bit of Fry and Laurie. Though a graduate of the same school of comedy, Thompson elected to bend the rules by doing without punchlines. She duly found herself on the wrong end of a critical handbagging. In the intervening decade, a lot of winking deconstruction and postmodern nudge-nudging has flowed under the bridge, and nowadays Big Train can take for granted a knowingness in its audience that Thompson could not. It can take a relaxed attitude to sketch convention only because others have died in the attempt.

Big Train is written by Graham Linehan and Arthur Mathews, the absurdists who brought you the clergy of Craggy Island. When asked to explain the name of the new sketch show, their stock response has been that Big Train isn't big, and it isn't a train. That seemed to be all the explanation we were going to get, but then came a flagship sketch in this week's second instalment. A female government minister is poring over a map of Britain with a man bidding for a rail franchise. When he pushes a scale-model train from London to Edinburgh, she is impressed at the amazing speed of the journey. He carefully explains that in real time the train would actually take three and a half hours. She then insists that to win the franchise the trains would in fact be the size of a normal train. But a full-size train, she argues, will have to pushed by a giant.

The sketch reads like a mission statement: we mine for comedy in the cranny between logic and illogic. Linehan and Mathews have been here before in the character of Father Dougal, who ruthlessly patrolled the boundaries of his own credulous world view. In so far as you never know where you are in Big Train, you know where you are. You think you're in a sketch about a ban on office smoking, except that the word "smoking" has made way for "w******".

Despite the odd announcement of its demise, the sketch show has never really been away. It will always attract a certain type of comedian, one who is better at writing than acting. Victoria Wood cut her teeth on it. French and Saunders occasionally return to the well. Reeves and Mortimer are currently filming their first sketch show in three years. An entire generation of grub-street gag hacks keeps itself in beer money selling skits to various outlets. Big Train's sketch about the sweatshop of underage pun-writers sailed to within hailing distance of reality.

If the sketch is in robust health, it's thanks mostly to the traditional cartoon grotesques dashed off by Harry Enfield and Chums and its hyperactive kid brother, The Fast Show. Like Dick Emery, or the Beano, both shows rotate a regular cast of caricatures. The pleasures on offer are based on fulfilling expectation, like munching through a pack of Opal Fruits: there's some unpredictability, but not too much. The joy of Big Train is that it has removed that safety net. To be fair, there is one running gag, but it's one which slyly comments on the excesses of the sketch format. The 43rd World Stare-Out Championship is the only cartoon in the series. Compare Enfield and Paul Whitehouse, with their sackful of catchphrases made flesh. The championship brings a sterling self-parody from Barry Davies, who this week did a lovely turn corpsing at his own double entendre.

The stare-out contestants remain impassive even when a streaker runs past, and in the rest of Big Train you can't see the actors blink either. When a sketch calls for ham, the cast provides it, as when the evil hypnotist cures a woman of addiction to smoking where two ordinary hypnotists fail. But in general the ensemble acting serves the brilliance of the writing by selflessly underplaying. That's another reason why it's called Big Train. There are no egos, and it isn't a vehicle.

There can be a tradition for shows like Big Train to subvert only if elsewhere the tradition is maintained. Goodness Gracious Me, which began a new series in the same week, fulfils that brief. It is now into a second stint cracking jokes about Asian stereotypes. Some of them may be very funny, but they are cracked according to the Opal Fruit formula. Meet the Indian grandmother who sours the lives of her children and children's children: the Indian mothers who brag about their sons; the two-bit Indian Lothario who insults all his dates.

The originality is in the content, rather than the container. But for all its freshness, Goodness Gracious Me looks vulnerable to the law of diminishing returns. Some of the jokes are starting to get repetitive. Have you heard the one about how all Anglo-Asian men are doctors? Yes, about twice an episode.

And however large the Asian population that underpins the ratings, the indigenous portion of the audience may well tire of being told how patronising they are. An Indian saying "Anyone fancy an English?" deftly makes the point that culture does not boil down to cuisine. This week a sketch made the same point more heavy-handedly. At an editorial meeting of the Indian Broadcast Corporation, a representative for minority programming proposes a series about Britain that would attack the national stereotype.

"What about an all-British comedy show?" retorts his Indian superior. "Anything in an English accent is bound to get a laugh." "Jolly quite right," says a colleague. They all laugh, apart from the Englishman. That looks like biting the hand that feeds you. Goodness Gracious Me is much funnier when it laughs at its own.