I like it, I'll take the lot: There is pleasure, profit and pain in catching the eye of Charles Saatchi. Simon Garfield reports

THESE DAYS it's as if he rides a white charger around the galleries of Mayfair, King's Cross and the East End. Many dealers and artists see him as the saviour of modern British art - inexhaustible, passionate, obsessive. But he is not buying conventional work; the stuff he likes makes the Tate's bricks by Carl Andre look like Rembrandt.

At a time when the contemporary art market is almost dead, with galleries closing every week and auctions realising a fraction of pre-recession prices, Charles Saatchi is still buying vast quantities of art. Every few months he walks into a gallery and buys an entire show, five or 10 pieces at a time. Painting, sculpture, traditional stuff, weird stuff. He buys a head made out of the artist's blood; a sculpture including live maggots and a peeled cow's head; a table with two fried eggs and a kebab on it. Last year he displayed a stunning piece of work by Damien Hirst called The Physical Impossibility of Death in the Mind of Someone Living. This was 21ft long and made out of glass, steel, silicone and a shark in formaldehyde. You can laugh, cry, or curse, but Charles Saatchi just keeps on buying. Precisely why he does this is an interesting question.

He has been collecting seriously for 20 years, and in the Eighties became the most active and powerful figure on the British art scene. He made a fortune: most of the young artists he favoured were unknown, but in the process of building up a huge collection of post-war work and making a fortune from it he turned many of them into stars. Some of these artists were fresh out of college.

When he sold many of his most valuable paintings - Warhols, Lichtensteins, Twomblys - at the start of the recession, rumours spread that he was splitting his collection, getting out of art. Now it appears that the opposite was the case: that in the face of the recession he was 'refining' and 'de-acquisitioning' in line with his changing tastes.

But, whatever we think of the work, the ambivalence about his role in the art world persists. Some people like to see him as a cultural crusader in search of beauty, truth and an explanation of the human condition. Others accuse him of wielding dangerous influence over artists' careers, of exercising a stranglehold over the modern market. They believe he is only in it for the money.

LAST MONTH Saatchi made another young man's day, if not his career. He had accepted an invitation to 'Strictly Painting', a group show of seven artists at the Cubitt Street Gallery, near King's Cross. He saw new work by David Leapman, whose last big show he had bought in its entirety. He admired pieces by David Austen. But what he really liked was the large, dense blue-grey oils by 32- year-old Simon Callery.

A few weeks later Saatchi visited the Anderson O'Day Gallery where Callery had a solo show. Saatchi bought him out, five paintings for about pounds 20,000; the news made the Independent's front page. Saatchi demands a big discount, partly because he buys in bulk, and partly just because he's Saatchi.

'In former times, his demands for a large discount could have been a deal- breaker,' says one dealer. 'He can make himself very unpopular with these demands.' Out of that pounds 20,000, Callery probably gets less than half. Not a lot of money for a lot of work, but Callery knows that with Saatchi you get more than just a cheque. You either get fame, or you get pain.

Many artists in the Saatchi collection will tell you the tale of Sandro Chia, the Italian figurative artist, who was bought in bulk by Saatchi in the Eighties, and then swiftly sold. Chia was dumped by his gallery, the value of his work fell, and for a while his career was in free fall.

If Saatchi holds the bulk of your work, then inevitably your fate lies in his hands. He can exhibit you, sell you, or crate you away in the dark. This control would be fine if he owned just a few pieces. But what happens if he owns 15 of your works and gets bored?

'Mr Saatchi is not an art collector, he's an art dealer,' says Sean Scully, a painter who was bought and sold by Saatchi in the Eighties. 'It's incorrect to call it a collection. It is correct to call it stock. An art collector is somebody who buys work to keep. That's not to say they will never sell a work, but they don't buy in at the bottom of the market and then sell into a rising market, which is more or less what Mr Saatchi does. Things he can't sell he'll give away for public relations.'

Scully remembers that Saatchi bought 11 of his works - arresting, fortress-like abstract oils - between 1983 and 1986. They were photographed after purchase and then packed away for storage. The next he heard of them they were on their way to a dealer in Switzerland. 'Your work ends up in stock until a good offer is made,' he says. 'In my case, he bought 11 works for dollars 250,000 and sold them for dollars 4m two years later.'

At 47, Scully is accustomed to this procedure. He does not wholly disapprove of Saatchi, and acknowledges that his reputation as an artist benefited greatly from Saatchi's interest. He believes his experience is a common one. 'He collects like a huge vacuum cleaner, sucking everything up,' he says. 'You can't contain these things. Art relies on money, and it relies on people with excessive personalities being involved. Art is extreme, so it necessarily attracts extreme people. And not all of them are going to turn out well.

'But Charles Saatchi is a natural consequence of art. If you make extraordinary things, you must expect to attract similar people. You're not going to attract some placid accountant from Surbiton. You'll attract people who are cosmopolitan, ambitious, egotistical, with a lot of psychological tension in their personalities. He's not the only type of lunatic out there who's an obsessive about art. They're all like that. But most of them are in America.'

Damien Hirst, though only 24 when bought by Saatchi for the first time, was wary of these pitfalls; consequently he is still regarded as a Saatchi star. Saatchi began buying his work in 1989 and in the next three years bought and displayed some extraordinary work - medicine cabinets, the maggots, the shark - and his patronage helped him on to the Turner Prize shortlist; Hirst became as close as the British art world had to a pop star. But in consultation with Jay Jopling, his agent, Hirst exercised close control over the works he sold and to whom he sold them. He was loquacious too: 'I was becoming this sort of Damien Hirst character,' he remembers. 'I was this slightly mythical thing.' Hirst is talking on the phone from New York; he says it was important to get away.

Hirst says that when he was at Goldsmiths' College he believed that being bought by Saatchi 'was one of the great things that could happen to you. But there were a lot of other people at college who said they'd never sell work to Saatchi. People accused me of having no integrity. They felt that if you attached money to art it was wrong. I remember thinking long and hard, 'Oh God, what's wrong with me?' But then I found that when Saatchi expressed some interest in these students' work, and bought a couple of pieces, all that suspicion or loathing disappeared pretty fast.'

Hirst was also aware of the 'Saatchi effect'. 'There are a lot of people who buy work just because Charles buys work. There are a lot of 'ear' people in the art world who buy because of what they hear rather than what they see. They're influenced by the scale at which Charles buys - it's a very sexy kind of thing. When I was at college I remember thinking when he bought Grenville Davey's work, 'Wow, he's made it', and then it was true: suddenly Grenville was showing all over the world.'

Inevitably there's a down side. 'It could be that no one else may touch them after Saatchi,' says Richard Wilson, a sculptor responsible for a vast installation of black oil in one wing of the Saatchi gallery. 'They might be unsure about what sort of artist they become. A curator may feel that they're showing power by deliberately not following suit. Not doing what Mr Saatchi does can be a powerful statement.'

Saatchi seldom meets the artists he buys; in fact, he rarely talks art at all, especially not publicly, and particularly not with journalists. 'That's the difference between Saatchi and others,' Sean Scully says. 'He was always remote. There are some big collections of my work. The people who own The Gap have about eight of my paintings, and when I see them we talk and they're interested in what I'm doing. But there was never anything like that with Mr Saatchi.'

Other artists find this reclusiveness beneficial. Suzanne Treister, who has five paintings in the collection, says: 'A lot of collectors go to openings and buy work because they like to feel that by doing this they're buying the artist as a friend. Saatchi just wants the work and doesn't want to buy friendships, for which I'm grateful. I had one other collector who actually wanted to sell something back to my dealer because I wasn't speaking to him. He somehow thought he'd bought me.'

SAATCHI, who will be 50 in June, not only has a huge collection but also a huge gallery. It is almost as withdrawn as its owner. The only clue to its existence in a north London street is a tiny label by the buzzer. It is only open to the public on Friday and Saturday afternoons (admission is free).

Sarah Kent, the art critic of Time Out, who wrote the catalogue notes for the current show, says: 'His gallery is a model of what a contemporary art gallery should be - it's beautiful and shows work that is confrontational and radical. He says that he believes in his work by the way that he shows it. Compare that with the way the Tate operates: in every respect it says 'We don't believe in this'. It's always apologetic.'

If you doubt Saatchi's taste, a visit to his gallery may alter your perceptions. 'Young British Artists 2', his new display, features some of his most exciting discoveries. Exhibits include the blood head by Marc Quinn, which is made of dental plaster and filled with nine pints of the artist's own plasma (drained from his veins over a period of five months - he could have done it all at once, but he wouldn't have made the private view).

Then there's the eggs and kebab, rotting, by Sarah Lucas, who also has some enormous paintings of blown- up tabloid sexploitation. There are some paintings of stallions by Mark Wallinger in an adjoining room to his full-length portraits of Thatcher's underclass - homeless men and women carrying bottles and bags, dishevelled, exhausted and fiery. From these you might walk to Rose Finn- Kelcey's Royal Box, a walk-in freezer with an ice-cube sculpture inside.

The show is vibrant and youthful (all the artists are in their late twenties or early thirties), and it is almost impossible to like or dislike everything. Last Saturday was busy; visitors pointed and talked, and you couldn't help but feel that you were at an event.

The show is controversial, but Saatchi has always been a tempting target. When the gallery opened in 1985, critics worried about the power Saatchi wielded as a definer of taste and accused him of using his museum-like showroom as a 'legitimising' space; if his purchases were shown in such ideal surroundings, and hyped by the media, how could their value not increase?

'Criticism of Saatchi is entirely to do with the fact that he isn't an establishment figure,' Sarah Kent says. 'He's largely an outsider (he was born in Baghdad), and the art establishment can't bear that, can't bear the fact that he isn't one of them and doesn't have a smart accent.'

Kent believes that having work in the Saatchi collection can be as important as having work in the Tate, if not more so. 'It's certainly a more accurate barometer of post-war art. The Tate has real problems buying contemporary work because (its director) Nicholas Serota's hands are tied. At the moment there is this terrible hostility towards almost everything produced this decade.'

In the early Eighties, Saatchi lent the Tate Gallery a lot of his work and received terrible stick. Critics claimed it was a cynical financial move and accused him of trying to increase the value of his holdings by seeking the Tate's validation. Now he rarely lends his work. But how could a national state-funded museum buy or even display the works that Saatchi favours? Two fried eggs and a kebab in the Tate? You can see the pickets attacking the delivery van.

But even at the Saatchi gallery only about 20 works are on display at any time. A few others hang in Saatchi offices in London and New York. About 1,000 works are locked away, many in East End warehouses. These works are waiting for something to happen.

SAATCHI's tastes and practices have changed a lot since Doris, his first wife, encouraged his interest in collecting things other than comics, cars and juke-boxes in the late Sixties. Doris was an eloquent American art critic who adored minimalism and the New York braves: together the couple bought at the Lisson Gallery in London, toured the lofts of the SoHo in New York in search of a form they hadn't found in Britain. They bought Warhols, Carl Andres, Frank Stellas.

Attention then switched to Europe, where they bought Anselm Kiefer, Georg Baselitz and Francesco Clemente. In the mid-Eighties came another fundamental shift, a passion for the Brits. British artists had never been ignored, but neither had they been bought by the truckload. Saatchi's shifting tastes may have had something to do with his separation from Doris in 1987.

Saatchi bought established homegrown talent such as Lucian Freud, Howard Hodgkin and Leon Kossoff, as well as the less well-known Hirst, Rachel Whiteread and Grenville Davey. Many of these new artists enraged and baffled the establishment, just as Saatchi's earlier passion for Jeff Koons's basketballs in tanks had done; just as Julian Schnabel's smashed plates had done.

His hunger for art seemed to increase directly with the success of his advertising business. It is no coincidence that his most expensive purchases followed the successful share flotation of 1975 and the boom years of the Eighties. But having risen to fame through its Conservative election accounts in 1983 and 1987 ('Labour isn't working'), the Silk Cut slit-silks and the 'pregnant man' campaigns, the agency is now in the recovery room after intensive surgery.

Much of the art he has sold in the past three years has come directly from the smaller collection he built at his agency; this month's annual report shows that work valued at pounds 1.8m was sold from the business last year.

Still no one buys like Saatchi. 'Recently he's bought a lot of work that I think is awful,' Hirst says. 'Sometimes I think it's like a huge net - if he buys enough work for a few thousand pounds now, then surely some of it is going to go for pounds 100,000 in five years' time? I think he's just really compulsive; if he sees it, he's just got to have it.'

Bernard Jacobson, a London dealer who is the same age as Saatchi, cannot understand his friend's interest in this work either. 'I suppose that some people are looking for eternal youth. It's not substantial work, and there is no point in buying art that isn't good. There are so many 'isms' at the moment, like one every 10 minutes. I'd prefer Walt Disney cartoons.'

At the moment the art world is a bit like horse racing, with the few people who are still buying searching feverishly for a winner to bring them a fortune. Saatchi's success in the Eighties was partly responsible for creating this fever. But what sort of art world would we have without him? He may be contemporary art's only hope. A rich man who likes this crazy stuff is hard to find.

The Saatchi Collection: 98 Boundary Road NW8; Fri-Sat 12-6pm; free.

(Photographs omitted)