TELEVISION / Dusting down the mental furniture: Kevin Jackson spends A Night In with Alan Bennett, wondering Whatever Happened to the Likely Lads? and recalling Abigail's Party

WHEN they first appeared in British homes, Alan Bennett recalled, television sets were done up in heavy wooden disguises - pretending to be something less vulgar, such as gun cabinets. The old-style set might thus be thought of as a visual euphemism rather like the commode: 'Looks like a chair, actually it's a lavatory.' The playwright used this phrase as title for his introduction to A Night In with Alan Bennett (BBC 2, Sunday), a ploy which could itself be seen as an act of camouflage. It suggested something quaint and comfy, yet soon proved to be full of anger and personal barbs: looked like a chaise longue, actually it was an Iron Maiden.

Bennett's chief objects of rage were the politicians who have the power to control and maybe wreck British television even though they look at its output with much the same frequency and enthusiasm they would grant the contents of a working commode. In Bennett's view, this is not merely cynical but amounts to treating the viewing public as a public convenience, and from a great height at that.

Clearly suspecting that such bolshy talk would get up the noses of at least some of his constituency, Bennett tagged each of his ruder remarks with a comic aside, in which he would swivel towards the camera and talk back to himself in the querulous tones of Mr or Mrs Outraged of Esher. These were the only ill-judged moments (they made him look a bit touchy) in an otherwise splendid amalgam of rumination and polemic, which ranged widely and effortlessly from the old writer-mooching-around-slagheap cliches of arts documentaries to reflections on the fragility of our collective memory.

Though most of the clips Bennett used to support his arguments, or just for pleasure, tended to be a couple of decades old - Larkin and Auden, Morecambe and Wise - the most emblematic of them was recent, and from that eccentric series of mini-lectures on art which gleefully confound the usual categories of high culture and fodder. Rab C Nesbitt, for it was he, asserted the essential realism of Rene Magritte's The Lovers by pointing out that Mrs N preferred to slip a bag over his head when he was on the job.

Lord Reith probably would have fainted dead away, and yet the impulse behind these stunts is recognisably in his tradition, and so was Bennett's talk. Even if you swallow the dubious proposition that the viewer is a consumer, he maintained, it is the job of television to be a proper supermarket, which stocks its share of quality goods and helps its customers check them out. There may have been some gaps in this argument, but it added up to one of the most eloquent defences of the Reithian line in a good while, and the most entertaining.

At the very least, it toned up the sensibilities a treat for a few hours of archive-shopping that followed, including a 1973 edition of Whatever Happened to the Likely Lads? that showed how Dick Clement and Ian La Frenais's writing can trample on the majority of notionally serious dramas, let alone rival sitcoms. How often do you see a scene as funny and emotionally complicated as the one in which Terry passionately evoked the spirit of Jarrow while Bob poked defensive fun at his rhetoric? Almost never, unless there happens to be a Mike Leigh rerun on offer, such as Abigail's Party from 1977.

In the wake of Bennett's cultural ponderings, the most telling aspect of Abigail's Party last night was the character of Lawrence (Tim Stern), the harassed estate agent who tried poignantly to cling to his few scraps of high art - the unread Shakespeares 'embossed with real gold', the Van Gogh print - both as tokens of a more compendious life and as cudgels with which to batter his ghastly wife Beverly (one of Alison Steadman's most deathless monsters). At once the funniest and cruellest of its scenes came when Lawrence forced his guests to listen to Beethoven's Fifth. Another emblematic moment, and an object lesson in how not to bring art to the masses.

Elsewhere on BBC 2, Teenage Diaries (Saturday) carried on doing its bit, as Bennett put it, to introduce the nation to itself with 'Julie Through the Looking Glass'. This confession of a 17- year-old, 33-kilogram sufferer from anorexia nervosa had a grim topicality in the light of last week's headlines, and gave some of us a first opportunity to witness the often-cited, science-fictional sight of an emaciated girl bemoaning her non-existent poundage and wobbling her non-existent flab. A nasty experience, but not as enlightening as it might have been, since the diary format more or less precludes analysis, and the true causes of Julie's illness still seemed vague when the end credits rolled.

In advance, it seemed like a tempting idea to use Teenage Diaries as a stick with which to beat the glossily vacuous teens of Beverly Hills 90210 (ITV, Saturday) - viewed purely for the purpose of comparison and analysis, you understand. And yet among all the teen agonisings about credit cards and backstage passes was an older character, a Jewish lady who had fled Europe to escape the gas ovens that this historian fellow assures us never existed. A small concession to service broadcasting, no doubt, but in view of the percentage of American high school children who are said (and 90210 makes it easier to credit) to think that the Holocaust is a Jewish holiday, a welcome one. Even pap can sometimes show a conscience about collective memory.