Really, Mr Grayson] Your moustache may be immaculately clipped, but I happen to know your dapper three-piece, chalk-stripe suit was bought secondhand in Brick Lane, east London, for a paltry 20 quid. I saw it last week on a rack of costumes reserved for your mentor, Harry Enfield, behind the counter in an industrial unit containing the country's biggest collection of contemporary men's hire costumes.

As for your black tie with cream double stripes (Brick Lane, pounds 2), does it betray a streak of violence? I only ask because, in between Mercury television commercials, it was worn by a bank-robbing character in a Tennent's lager commercial.

Real-life robbery is a headache for Carlo Manzi, 46, who launched his hire business 12 years ago after a career as a freelance costume designer for television commercials. The words 'Own Up' are painted in 2ft-high red capitals at the entrance to the hangar-like interior in West Hampstead, north London, where 30,000 costumes are stored. Vintage clothing buffs have been known to be reluctant to return trendy bikers' leathers, battered old trench coats and expensive brogues.

Violence is a problem, too, although he has only to switch on the television to check if his stock is having holes punched in it to accommodate a stunt man's flying harness. 'I do recognise my clothes on television,' he said, 'in fact, I can remember what sizes they are and who else has worn them.' Mr Grayson's tie will not be going on any more holidays. Too worrying. Mr Manzi parted with it only because the costume designer for the Tennent's commercial panted 'I love it]' It arrived back in the nick of time for another Mercury shoot.

Visitors soon get an inkling of why his double-decked racks of gear - 'a private collection got out of hand' - arouses the hot flush of fetishism. He steered me towards the leathers: Forties-style German and Dutch calf-length border guards' coats, so chunky they looked as if they could stand up on their own.

'Feel the weight,' urged Mr Manzi, lifting one out, 'it's a bit like wearing a cow - not the kind of thing a dealer could sell to your average punter. These things go out a lot for rock videos of bands that want to look sexy.' The coat is worth about pounds 200 in the trade. Specially made, it would cost pounds 600.

On to the bikers' rail. 'We've got some great top-of-the-bale stuff here.' Top of the bale? About a dozen big British vintage clothing dealers buy bales of secondhand clothes by weight from Germany, the Netherlands and Belgium. Wool bales, suede bales, leather, hippie and denim bales. Hippie bales no longer contain denim: it is valuable enough to be baled separately. Hippie now means post-

punk Gothic gear such as turn-of- the-century black frock coats, worn with white face make-up.

'Look, this is gorgeous]' Gingerly, he lifted down a 20-year-old Barbour wax coat. 'Just look at the state it's in. You couldn't send that out to be distressed and get it back like that. It had to be worn.' He bought it for pounds 20 from a dealer who told him it had belonged to a vole catcher. The coat was creased into ridges, stained and scuffed, and the inside lining had been worn away by heavy objects in the pockets. Voles, presumably. 'Fabulous. I'd like a rack of those. Come to think of it, I've got a rack of those.'

Do Britain's vole catchers and tatterdemalions beat a path to clothes dealers' doors to sell their cast-offs? Hardly. The go-betweens, Mr Manzi explained, are rag-and- bone men. They know the value of distressed top-quality clothing.

Costume designers routinely ask Mr Manzi's permission to distress his stock. 'Can I have it broken down to rough - or even very rough?' they ask. (My overcoat, parked disconcertingly on Harry Enfield's rail by Mr Manzi's staff, was classified by them as 'worn but not rough'.)

I later spoke to a distresser, reputedly the best in the business. Alex Carey's visiting card describes him, less dramatically, as 'specialist in painting and decorating fabrics and costumes'. He will 'characterise' a costume in one of 10 grades, from 'extra-subtle, almost new', to 'almost disintegrating' - taking care, of course, not to drag a costume through a bog if the character is supposed to have been crawling through a desert.

There is nothing destructive about the sandpaper, wire brushes and cheese graters he wields, or the methylated spirits and FEV (French enamel varnish). This is art. 'It's like painting in 3-D,' he said. He regularly roughs up the Glyndebourne Opera, Madame Tussauds and Blackadder's disgusting sidekick, Baldrick.

And if you think Compo's tight- fitting jacket and baggy trousers in Last of the Summer Wine have 'gone too far', you now know that his distresser, Mr Carey, agrees. Trouble is, Compo needs at least three identical versions of his garb: a spare for his stunt double and another to continue filming in whenever he gets soaking wet.

Meanwhile, back at the hangar, Mr Manzi and one of his three staff are puzzling over which tweed flowerpot not to choose from a job lot of 50 which he now regrets having had cleaned. 'How knackered do you want it?' he asks. 'What's the character supposed to be?'

'Old bloke. Urban poor.'

Whose commercial is it, I want to know. 'McDonald's'

Pinned to the wall is an incongruous group photograph of faculty and students of Imperial College's department of chemical technology in the academic year 1938-39. Rows of bespectacled boffins. One clenching a pipe between his teeth. Mr Manzi says: 'I put it there to show people how varied style can be. They may say, 'It's set in 1940, so I want only two-button or one-button suits'. But look here - you've got one-button, two-button, three-button, single-breasted peak lapel, single-breasted notched lapel, double- breasted, two-piece, three-piece, shirts with stiff collar, shirts with soft collar.'

Why rely on clients for ideas when you can create styles of your own? A damaged modern Herbert Johnson trilby which Mr Manzi decorated with assorted badges - Berkshire Constabulary, gold and silver anchor, an ivory and silver pendant, tin numerals - made it into Italian Vogue last year. 'A good grunge hat,' he said proudly.

What might be called his bread- and-schmutter are 'basic executive' suits: Armani, Ralph Lauren, Jasper Conran, Yamamoto. But none gets as many outings as a 42in Second World War American aviator's horse-hide jacket that seems to fit every actor cast as film director, photographer or young hero. It is hired about 30 times a year.

Denise Simmons, the freelance costume designer who paces the racks with Harry Enfield whenever he is pondering how to bring a new character to life, breezed in to look at a couple of green Melton sports jackets ordered for the disc jockey David 'Kid' Jensen. In a televised montage of their careers as wayward disc jockeys, to be screened in August, Nicey (Harry Enfield) and his pal Smashie (Paul Whitehouse) will see Jensen's stunt double kicked downstairs wearing one of them.

Television entertainers spend much of their lives agonising over costume. Most of them are connoisseurs of the technicalities of distressing. Lenny Henry paid particular attention to a tracksuit he wears in his role as a schoolteacher on a run-down council estate in White Goods, a two-hour television film for Meridian Broadcasting which started production this week. His instructions: 'When you think you've broken it down enough, do it three times more and it'll be fine.'

That suit of Mr Grayson's could do with enhancing instead of distressing if it is to preserve its crisp, Fifties look. But how do you give a commercial's exposed film stock a period flavour? The first Mercury ads were shot on old stock which was then dragged round the cutting room floor. Now there's a thing: distressed film.

(Photographs omitted)