TELEVISION / A vintage lot on view in the auction room

HOW HELPFUL of two rival channels, usually so bent on trumping each other, to co-operate for our benefit. Under the Hammer (ITV), a drama series set in an auction house, went on view within a week of the BBC's Auction, a documentary series set in an auction house. Audiences thus have an opportunity to assess for themselves the similarity of the copy to the original.

You don't need sophisticated X-ray equipment to conclude that the later work, clearly revealing the broad brushstrokes of a prolific late 20th-century artisan known as Giovanni Mortima, isn't an authentic portrait of a saleroom - he does courtrooms better. As with anything from his workshop, though, there's still a good deal of innocent pleasure to be drawn from it.

For a start, the shirts aren't nearly stuffed enough: when at the start Ben Glazier, raffishly played by Richard Wilson, arrives for work on the morning a long lost Raphael goes under the hammer (and that smacks of high-flown invention too), he's on a monstrously large motorbike. And what's more, the employees of the fictional Klinsky's look far too well-heeled: Glazier's colleague Maggie Perowne (Jan Francis), lives in a sumptuous flat plastered with valuable works; they say you need a private income to be able to afford to work at Sotheby's, but there are private incomes and private incomes.

Part 1 was called 'A Fatal Attribution'. Just this Christmas we had an 'Only Fools and Horses' called 'Fatal Extraction', which just goes to show that writers use all their creative juices before they get round to subtitling, but we'll let that rest. The drama with which 'Under the Hammer' really bears comparison was 'A Question of Attribution', Alan Bennett's absorbing study of Anthony Blunt. Here, as there, it was the authenticity of humans as well as paintings that was probed under the microscope.

A Bronzino had materialised in the home of a dead restorer. His sparrowish widow (Susan Wooldridge) didn't bat an eyelid: 'Was it painted by a very clever person,' she said to a slavering Wilson, 'or does it give you pleasure?' The question was asked but not answered, because an authentic John Mortimer script is far too busy painting caricatures to debate ideas. You could tick off the usual suspects - the doddery aristocratic airhead, the cultureless Thatcherite company chairman, the swinish Hooray in the wine department, John Gielgud's randy octogenarian aesthete. Nice to see them all again.

When Woodridge bicycled under an HGV we had a body to show for all this ambling observational comedy. A drama that portrays death as a bit of a jolt is always more accurate than one that treats it as part of the furniture, but you were left not knowing whether you should have chuckled at all that had gone before. The same thing happened in 'Intolerance', an extraordinary film for Cutting Edge (C4), which toured the nation in search of neighbours who don't ask each other to water the plants when they're on holiday.

We started dramatically with the Pitt family - a matriarch, several Rottweilers and even more offspring - who lived under siege on a Northumberland council estate and came straight out of Zola's Germinal. After that, most of the tales of petty enmity raised a smile, or at most a shiver of schadenfreude, but like the oeuvre of Alan Ayckbourn it got darker as it went along: we ended with murder, motivated by an argument over a boundary fence.

You felt guilty for having enjoyed the previous absurdities - squabbling Plymouth neighbours who used the camera team as a kind of arbitration service; a Croydon crank with a tank on his lawn; a Derbyshire spinster who complained about the rifle range across the yard. You could see the bullet marks all over her neighbour's blue barn door: 'They say they're shooting rats,' she said, 'but there aren't many rats that measure a height of six feet.' Not unless they're human rats.

Thomas Sutcliffe returns tomorrow