Review

How's this for nerve? You launch the first episode of your new sitcom with a plot which includes an embarrassing dead body, a health inspector and a dead rat in the water system. What's more, the body language and vocal style of your chief character, a splenetic deputy-head teacher, owe more than a little to John Cleese (an impression further confirmed by memories of that actor's performance as a headmaster in Michael Frayn's comedy, Clockwise), and the long-suffering female lead even bears a teasing resemblance to Connie Booth. It's little short of amazing, then, to report that Chalk (BBC1) isn't crushed to dust by the comparison it virtually begs you to make. If it isn't quite another Fawlty Towers (how likely was that?), it is more than promising and delivered with a degree of craftsmanship which regularly-burned audiences have learnt not to take for granted.

Chalk begins with the introduction of a new staff member into Galfast High, an institution which blends a vaguely realistic setting with a surreal liberty in its action - the headmaster, for example, is first encountered conducting a religious studies lesson from inside a cupboard, as a kind of practical demonstration of the invisible authority of God. Unfortunately, his class, which he believes to be unusually well-behaved, has long since decamped, having locked the door first. He is thus forced to conduct his induction interview with the new recruit through a skylight above the door - a fact which undermines some of the conventional cliches of welcome: "If you have any problem, of any kind whatsoever, my door is always open," says John Wells's headmaster blithely, his nose scraping on the lintel. In other words, if you were hoping for a wry comic treatment of the real issues afflicting the nation's schools, you had better go elsewhere; this isn't a pedagogic version of Cardiac Arrest.

What is heartening about it, though, is that the machinery all works, without any of the gimcrack bodges that have become so familiar in British sitcoms. Steven Moffat's script is not just capable of good lines, but also knows how to milk a few extra laughs from them. "Right, sit there and make a plasticine model of God," barks Mr Slatt (David Bamber) at an errant pupil, "and you'd better get it right!" The joke returns later, but so glancingly that if it fails, it barely matters - the repeats are offered as background details of character rather than centre-stage gag lines. Other staples of the sitcom form, such as the cross-purpose conversation, are offered in versions that don't actually gape at the seams, as is so often the case in mediocre comedies. Faced with the distraught neighbour of an English teacher who has died at his desk, Mr Slatt is under the impression that he is placating a health inspector worried about rats. "Look, the good thing is he's no longer poisoning the pupils' water supply," he replies, puzzled by the woman's inexplicable tearfulness. But what was he doing in the science lab, the woman asks. "I don't know," Bamber replies with mounting exasperation, "I expect they were doing experiments on him or something." Within the logic of the farce - a realm which has nothing to do with the real world - the misunderstanding is juggled from hand to hand without a fumble.

It helps that the series is strongly cast, with performers who can make comic exaggeration look controlled rather than merely pleading, but the solidity of the construction is what really makes it work. The script is even capable of rescuing an apparently duff conceit. When he needs to smuggle the deceased teacher out from under the noses of his pupils, Mr Slatt orders them all to close their eyes and pray, a slightly unconvincing solution to a plot problem. But when one pupil peeps and shrieks out the truth about the rigid Mr Humphrey, the device is redeemed. "Right!... who prayed for that?" bellows Mr Slatt, going on the offensive in a moment of lunatic inspiration. The ghost of Basil Fawlty definitely looked on at that moment - and he seemed to be smiling.