David Chater

If the feedback I get is anything to go by, there are two things viewers dislike above all else. One is orchestral Muzak in wildlife programmes. The other is canned laughter in sitcoms. The latter is particularly bad because it sets up an old-fashioned style of comedy with one character dollying up a feed-line and someone else hitting it for six. Unfortunately this new sitcom, set in the laboratory of an English university, uses a laughter track. It is a pity, because the characters are an entertaining lot who would benefit from the chance to escape from this straitjacket of comic conformity, while Chris Addison - last seen on our screens in The Thick of It - has a wonderful line in engaging, deadpan delivery.

Anyone who watched the first two episodes of this three-part comedy may well be hooked by now, not least because it contains the funniest comic performances in years. Hugh Bonneville and Elizabeth McGovern are perfectly cast as the decent couple struggling to cope in a media world gone mad. Tom Hollander's turn as their friend the agent has a childlike innocence and vulnerability that make him immensely likeable, even as the obscene petulance spews out of his mouth.

If any theme has emerged from this range of Comedy Showcases, it has been to see how far the boundaries of taste can be pushed. Here, Stephen Mangan and Sharon Horgan play theatrical agents who have been bruised by past relationships and are now having an unsatisfactory nonaffair driven by his need to sleep on her sofa. He is traumatised with guilt for abandoning his children and she feels responsible for the death of her fiancé. Both are needy, only their needs are different. There is a good deal of snappy banter between the two, but Anthony Head as their boss steals the show as a pervy old goat out of whose mouth pours an unending stream of uncensored filth. It's like being confronted by an erection on screen - more amazing than shocking.

Big Train seems to be achieving belated cult status. There are several reasons for the delayed reaction, perhaps most notably the cast's subsequent successes: in the second series from 2002, which is showing this weekend, Shaun of the Dead star Simon Pegg and Green Wing's Mark Heap are joined by a pre-fame Catherine Tate and a pre-EastEnders Tracy-Ann Oberman. But it is the off-the-wall humour of the writers, Graham Linehan and Arthur Matthews, the creators of Father Ted, that really makes this one comedy repeat worth devoting a significant part of your weekend to.

There was a bad moment in the first episode of this series when it seemed as if Black Books might have lost its footing. It was loud and slapstick and too crude to be funny. But now it is right back on form, and this is one of the funniest episodes yet. Manny (Bill Bailey) places a bet on the Grand National, which turns Bernard (Dylan Moran) into a chronic gambler. Once again, it is the inmates against the world. For all that they torment each other, their pooled inadequacies act as a bulwark against customers, debt collectors - and just about everyone else.

After last week's episode, which worked hard for its laughter, tonight's is a far more relaxed and subtle affair. Bernard (Dylan Moran) and Manny (Bill Bailey) decide to write a children's book. Bernard's first attempt at entertaining four to six-year-olds consists of a 1,300-page saga about the relationship between an academic who survived the Stalinist purges and a daughter whose long and bitter marriage is collapsing. "You should never talk down to children," he says. The episode plays to one of the great strengths of the series - the antagonistic co-dependence that binds the main characters together. It is a wonderful return to form.