In the 80s money was the theme of art. Prices escalated, the dealer became a star, critics fretted over mammon, and artists - above all Andy Warhol, and then his little wooden boy Jeff Koons - gloried in finance. But by the end of the 80s money had lost its crispness; it was soft and saggy, like a too-much-handled fiver. In the art of the past 15 years cash has rarely been the subject. Death, decay, the sublime were the themes of the British art that defined the end of the 20th century; the horror of a shark swimming towards you through formaldehyde, the terror of a house become a sealed tomb.
The sublime was the aesthetic of these years, this art - and the sublime, as the 18th-century politician and thinker Edmund Burke argued, is about power. The origin of the sublime, for him, lies in our awe before a majestic, divine authority. Today it is an awe of art itself, or at least a desire to experience that awe; to be knocked over by art, to be kicked in the teeth.
But with this taste for the power of art has come something uglier, stranger, sleazier - a fascination with power itself. Every book and documentary and bit of gossip about British art seems to slaver over the names of those considered "powerful in the art world" - the "tastemakers", to quote one hideous title. It is as if, as the power of British art has fallen off since the glory days of the early 90s, we have found sublimity instead in the institutions that surround it. The art world has become a spectacle, and we wonder who is more powerful: is Jay Jopling, owner of White Cube, a more crucial player than Norman Rosenthal, exhibitions secretary of the Royal Academy? And the million-dollar question: is the most significant man in the British art world Tate director Nicholas Serota, or is it Charles Saatchi?
Among those who liken Saatchi to Conrad's terrible Kurtz is a leading British artist whose work is a treasure of the Saatchi collection. He said that going to the old Saatchi Gallery and seeing all the cartoons that had appeared in the papers about this artist, collected and framed by Saatchi, felt like entering the lair of the trader in Heart of Darkness. It was a terrible revelation, he thought, of how obsessively his work's public reception had been manipulated by the hidden hand of the collector.
Given my desire to confront this monster, I was disappointed when press stories started to make Saatchi sound more like one of us. There have been well-publicised changes lately that might explain his willingness to show a few people around his new gallery. Saatchi's relationship with Nigella Lawson is a surprise in every way, a shocking contradiction of his image. Is he, after all, to become part of the London media world? I was weirdly saddened to hear that he might be normal, even nice.
And it has to be said that a feeble "nice" is the first word to describe what he was like when I met him. Affable, courteous, and - I think genuinely - shy: it's not just a cover story, his shyness, even if it is something he is obviously used to saying about himself. Others feel the same. "He's nice, isn't he?" says the artist Jake Chapman - with his brother, Dinos, currently Saatchi's major enthusiasm, second only to Hirst. "He's basically a wide boy - he's a shark, he's a fucker, but he's nice." "Oh no, he's going to be angry with you again," objects Dinos. "All right - he owns a shark, he owns a fucker, but he's nice."
Nice. Is that all there is? For all his elusiveness, there's something expressive about Saatchi. First there is his smoking. He smokes a lot. And with a sigh he mocks me for not smoking - that is, he is a little self-dramatising about it.
Just like Hirst, who has said you shouldn't trust people who don't smoke. Smoking is a central image in Hirst's art. I stand with Saatchi peering into Hirst's giant ashtray filled with cigarette butts collected at the Groucho Club, a vast smooth white receptacle - as big as the marble bowl from Nero's palace you can see in the Vatican - and on its base, where you might imagine a fountain, this grey and brown morass, this sickening residue. Luxurious death. The room has just been cleaned to get rid of the nauseating stench.
Saatchi's emphatic smoking is a confirmation that he profoundly identifies with Hirst, the artist above all others for whom he confesses himself a sucker. Art-world gossip has it that Hirst has fallen out with Saatchi. But if there is a froideur, it's not on Saatchi's side; he can't stop talking about how great he thinks Hirst is.
If the smoking suggests Hirst's imprint, it is also autobiographical. Saatchi's first famous ads, for the Health Education Council, included a series of unprecedentedly explicit anti-smoking posters. One showed a stream of black tar being poured into a transparent saucer. "No wonder smokers cough," read the copy. You can imagine the children who would become the Young British Artists seeing these ads on the way for a fag behind the bike sheds. Of course, Saatchi & Saatchi also advertised cigarettes - the ones he's smoking today, Silk Cut.
Saatchi is ritually described as the ad man-art collector, and Margaret Thatcher's ad man to boot. This is always brought up pejoratively. Not only is Saatchi a rightwing bastard, the line goes, but his shallow understanding of promotion makes him seek out crudely attention-grabbing art and push it in people's faces. According to this theory, Saatchi himself engineered the controversies over Sensation in London in 1997 and Brooklyn in 1998. In London Marcus Harvey's giant portrait of Myra Hindley made with children's handprints, and in New York Chris Ofili's The Holy Virgin Mary with its collaged pornography, seemed to catch the attention of the groups most likely to be offended by them remarkably quickly. That is, before the exhibition opened.
But above all, Saatchi's "influence" has been talked of in financial terms. He has been hated and feared as a man always ready to take out his wallet. He can buy museum approval, and he can bankrupt a reputation.
Most artists collected by Saatchi are reluctant to talk about this. Only a rare artist is able to ignore, or reject, Saatchi. Michael Landy, one of the artists in Hirst's Freeze (and a couple of years ago the recipient of rave reviews for a show in which he destroyed all his possessions), told me Saatchi was never a "supporter" of his work but did buy a sculpture of a fruit and veg stall, which he then sold. Landy recently got a call from Saatchi wanting to buy another version of the same stall for the County Hall gallery, "but I wouldn't sell it to him". He can't be bothered going through all that again - to be bought and sold.
In the 80s Saatchi's readiness not just to buy huge quantities of an artist's work but also to sell, with potentially huge damage to the artist, was even more feared than it is today. "I'm not so crazy about this thing of collectors buying and selling in bulk," says the Lisson's Logsdail. "I wouldn't say he's totally uncaring about it; when he realised what damage he could do by selling an artist, he was quite shocked. Since then he's done it more carefully."
Jake and Dinos Chapman are not scared of him - but then, they can afford to be cocky. Just before Christmas Saatchi paid £1m for the entire contents of their exhibition Works from the Chapman Family Collection, a museum-like display of pseudo-tribal artefacts, "primitive" totems shown in darkness. He is planning a big Chapmans show for the new gallery.
Several years ago, he almost destroyed them. In the mid-1990s Jake and Dinos Chapman were outrageous, entertaining manufacturers of perverse mannequins, and although they got a lot of attention, they never quite entered the canonical league represented at that time by Hirst, Hume and Whiteread. In December 1998 Saatchi sold a selection of his British art through Christie's; it was an event that caused the usual feverish speculation about Saatchi's intentions, his ability to make and break artists, even to end a historical moment. Was this how the British art boom would end - not with a bang but with an auction?
Whatever Saatchi's motives, the only artists who suffered from the sale were Jake and Dinos Chapman. The Chapmans' major sculpture Ubermensch (of Stephen Hawking in his wheelchair atop a rocky promontory) went for a humiliating £10,350, a tenth of the prices paid for minor works by Hirst and Whiteread.
The Chapman brothers were also ditched by their then dealer, Victoria Miro; they suddenly seemed an exhausted stock. They admit that they had no money, no future, and reached the point where they thought they would have to get full-time jobs - for which, they joke, being Britart stars didn't really qualify them. Instead they planned and constructed Hell, a tableau starring thousands of miniature German soldiers in a psychotic toy holocaust, and sold it for £500,000 to Charles Saatchi. The £1m they made him pay for their latest exhibition was "punishment", they say, for that £500,000 - which they thought undervalued Hell. This was in 2000, the year Saatchi paid the first six-figure sum for a Young British Artwork, Damien Hirst's Hymn. There were stories that Hymn's price was more notional than real. Jake and Dinos Chapman boast they got real money, all £1m of it.
When you start looking into the history of the Saatchi Collection since the 70s, and place it alongside the history of taste in the same period - the history at any rate of official art-world taste, the artists sanctified in museums and art magazines - it makes confusing reading. For a start, many people will be surprised there even was a Saatchi Collection in the 70s. In Saatchiworld, change is sudden, brutal and absolute: when the Boundary Road gallery closed its doors at the end of 2001 there was no fuss, no funeral, no flowers. That was then.
This is the most glaring eccentricity of the Saatchi Collection, and by extension, of Saatchi's sensibility - these massive, seismic, brutal changes of affinity. Saatchi seems, to judge from his collecting and his selling, to hate reassurance, to shun tradition; he has cut off his collection not just from history but, weirdly, from its own history. Today we associate the Saatchi Collection entirely and exclusively with the British art of the late 80s and since, ie the Hirst generation and younger. He claims not to have much time for previous British art - for example, 80s figures such as Julian Opie and Tony Cragg.
So I went and looked through some old catalogues - and found New British Art in the Saatchi Collection, published by Thames and Hudson in 1989, on the very eve of Hirstmania (a year after Saatchi says he encountered Hirst in Freeze). It contains a dignified collection of the venerable painterly heroes of an earlier School of London: major paintings by Lucian Freud, Frank Auerbach, Michael Andrews, RB Kitaj, Leon Kossoff, Malcolm Morley. And Julian Opie and Tony Cragg.
I asked Saatchi about far older art than that, about whether he had ever wanted to collect the Old Masters and thus become a more universally respected figure. He confessed to an interest in the subtle and spiritual Renaissance artist Piero della Francesca, but it is clear he could never be interested in collecting anything except the art of his generation. Meaning Hirst's generation. It's as if Saatchi - who is 60 this year - has so identified himself with this still thirtysomething generation, and with Hirst in particular, that he feels younger than he is. This empathy with youth crops up again as he shows me the room in which he will promote brand new artists, just out of college.
Saatchi, and he alone, pursues the absolutely contemporary - not just daring to buy the new, but seeking the newer than new, and showing it in complete seclusion from the old. It is as if what he is really trying to collect is something no one can bottle, not even Damien Hirst - the present moment, the moment that is always disappearing.
There are many who will find this a romantic and melodramatic way of talking about Saatchi, who is, they will say, just a human Hoover, a mechanical buyer, a vacuous spendthrift. For every good work of art he owns, there are 10 bad ones: how can you say he has taste when he likes the kitsch modellings of Ron Mueck (an artist whose career owes everything to Saatchi) and the dreary paintings of Jenny Saville? Does he even like art?
Having finally met Saatchi, I can say some things for certain about his sensibility - he does have one, though he himself denies it almost as vociferously as his critics. He is clever. More to the point, he is clever about art, in a way that makes the most hostile things said about him - including the idea that his ex-wife, whose magazine articles about art are far less interesting than his talk, was the true creator of his collection - seem absurd.
I suspect he is very au fait with contemporary art criticism. Saatchi makes it plain that visual pleasure, rather than the muted intellectualism of a certain kind of concept-heavy art, is what matters to him. The most cursory examination of the Saatchi Collection suggests this is true, with the qualification that visual intoxication for him comes from the grotesque as much as, or more than, the beautiful. I guess he has been reading the American critic David Hickey, whose writings, as it happens, endorse the sensuality of the private collector and "the big, beautiful art market" against what Hickey sees as the deadening "therapeutic" culture of public museums. Other things Saatchi says are more original, and reveal real passion, flowing in unexpected directions. He plans to put on an exhibition of the abstract expressionist Clyfford Still, a contemporary of Jackson Pollock who is overdue for recognition as one of the greatest American painters.
Given his reclusiveness, it is tempting to interpret Saatchi's collection itself, and his exhibitions, as a self-portrait. The old, white, hollow-skull Saatchi Gallery communicated a tangible fiction of Charles Saatchi as a remote autocrat. His new exhibition space says something else entirely. County Hall is warm - claustrophobically so - with wood panelling everywhere and long, umbilical corridors connecting organ-like spaces. At the heart is the old council chamber, restored and looking for all the world like the tribune of the Uffizi or an imitation by some crazed Victorian. And off the corridors, little offices of long senile or dead bureaucrats, each with a fireplace, are rooms painted white. In most, for this opening exhibition, is a solitary Hirst. While the former space denied history, this one rejoices in it. Saatchi spent two days with one painting, trying to set the lighting. The light, it seems to me, is singularly dusty and dead.
What the new gallery has in common with the old is spatial paradox. Here you get no sense of the structure around you; you're lost in a fantasy world. Except that where the first Saatchi Gallery was science fiction, this is gothic. Saatchi was bored with white space; it got so everyone was using a space like that, so with this he has deliberately set contemporary art in an old, eccentric context.
Most of all, Saatchi seems to feel the need for a palace. It makes his collection seem more aristocratic. And, it turns out, his own template of the art collector is an aristocratic one.
Saatchi's hero and model among art collectors is Count Panza, an Italian who bought a great deal of minimalist art and gave it to public collections: MoCA (Museum of Contemporary Art in Los Angeles), the Guggenheim. Saatchi is ardent about the greatness of this collector hero, always repeating that "Count" as if he was especially struck by this, by the aristocracy of taste.
Count Giuseppe Panza di Biumo - to whom the Lisson's Logsdail remembers introducing Saatchi in the 70s - is a major collector of the 20th century but, perhaps most strikingly, he set his collection in a palatial context, his Villa Litta in Varese, north of Milan. Today, the parts of his collection not in museums around the world are on public display there, in an extraordinary play of the minimal and the baroque, the contemporary and the old. Dan Flavin neon pieces and James Turrell light installations are in the stables; monochrome canvases hang in rooms with ornate rococo ceilings and curvaceous fireplaces.
And it is, or was, a home. It has the eccentricity of a home. This, I believe, is what Saatchi may be after. His new gallery has the scale of a museum but it has the personal, undesigned feeling of a home. There are fireplaces, clocks, little rooms where you can be by yourself.
Partly, he is giving the art a home - to stabilise it and let it settle down. He now seems unhappy about Sensation. The artists from it are in his opening show, but this will be a chance for a more thoughtful appreciation of their work. However, as Jake Chapman points out and as Saatchi himself is aware, it's a place where bad art will look really bad.
In terms of the myth it creates of Charles Saatchi, this is a home for him, too. Instead of having his own palace with art in it, he has bought one ready-made. Through Count Panza, this connects him with the kinds of collectors to whom he is sometimes compared; the Italian Renaissance princes, the Medici or Duke Federico da Montefeltro.
He really does envisage this as a place he will maintain in his old age. The Tate no doubt hopes that when he dies he will leave his great rival his entire collection. But the new gallery has a long lease, and he paints a vivid picture of himself being wheeled around here years from now, drooling.
The best thing here is Damien Hirst's A Thousand Years, a sealed transparent tank containing a severed cow's head and myriad flies, which create woozy and ever-changing black graphics until they buzz merrily into the insectocutor. It is an epic history of life and death in a godless universe, as ambitious as any art is likely to be for many years to come.
Hirst and Saatchi; Saatchi and Hirst. They are coupled for all time. Or for five minutes. It depends how Hirst is remembered, how he is rated by history. It would be completely wrong to think Saatchi values the other artists in his collection in the way he values Hirst. Hirst is what he stands or falls by, and he knows it. Saatchi's favourite Hirst is Away From the Flock (1994), with its little stray lamb innocent and forever young in its tank of greenish formaldehyde. He finds it, he tells me, an especially emotional work.
The opening exhibition, although it includes works by Chris Ofili, Sarah Lucas, Glenn Brown, Tracey Emin, Gary Hume, Marc Quinn and Ron Mueck, is primarily and authoritatively a Hirst retrospective. It's the first chance in London since 1997 to see the classic vitrines, to gawk at the pickled shark. (It now looks sadly desiccated, although when I walked towards its mouth and the refraction of the tank suddenly made it seem to leap towards me, I found the effect almost as daunting as it was more than a decade ago.) Here, for the first time, you can compare these early works with Hirst's anatomical sculpture Hymn and a new vitrine that has live carp swimming about. The tank also contains an office desk; it's a far more joyous subversion than the older vitrines. Also, there is a spin painting actually spinning - lovely to behold.
I agree with Saatchi that Hirst belongs in the same company as Warhol. Hirst is the definitive artist of the end of the 20th century; we have yet to see how he will shape up in the 21st. Hymn is a transitional work, a confession of a dead end, a joke about the fact that everyone thought the logic of his work was to pickle a human corpse. Of course it wasn't: he's an artist, not a psychopath, and the art in his art is beautifully formal and gracious in this context - the repeated blue-green tanks containing that sliced-up cow, the graphic networks of viscera against glass, the strong, bold, white metal frames, the grim joke of the bisected pig. Saatchi compares Hirst to the minimalist Don Judd. The shapes, the fearful symmetries.
"He's a shark", as Jake Chapman said. Damien Hirst already made the joke, visually. Charles Saatchi is no monster. But the Saatchi fictionalised by the Saatchi Collection is - a gorging consumer of art, swimming remorselessly up the Thames, towards Tate Modern.
Ah yes, Tate Modern. There is no doubt the tension between Saatchi and Serota is real, although they profess mutual admiration. It seems obvious to me that if the Tate wanted to make friends with Saatchi it would ask him to curate a show. He does not think of himself as a collector but a maker of exhibitions. It is showing, not owning, that matters to him. In this sense he is the perfect collector of post-minimalist art, because what he craves is precisely what the critic Michael Fried styled, pejoratively, the "theatricality" of the contemporary art object.
Saatchi is dismissive of the current Tate Triennial exhibition. I head over the river to Tate Britain, and find that Days Like These presents a very different picture of British art from that inside County Hall. It takes the attitude that we have moved on, that time has passed, that Hirst is history. The new art is - well, it's not much, on this showing. Some incredibly bad paintings by Dexter Dalwood (once a Neurotic Realist); some mesmerisingly good ones by George Shaw; an almost exciting colourful floor by Jim Lambie; a lot of mediocre video installations. Saatchi dislikes video art.
It's a doomed quest, it seems, this search for what comes after Damien Hirst. Saatchi himself came a cropper when he tried to identify post-Hirst art in his Neurotic Realism shows. Now, having put that in the dustbin of history and returned to A-grade Hirst, he can afford to sneer. But what is really missing from the Tate show, I realise, is the fleeting sense of the contemporary, the absolute present, that Saatchi endlessly pursues. At Tate Britain the contemporary seems to have moved on, though the exhibition only opened a few weeks ago. The deep appeal of contemporary art may be that it can briefly make us feel, if not like a community, then at least like contemporaries of one another: it releases us into an intoxicating present. Saatchi is our greatest scenarist of the contemporary. Art for him is news, or it is nothing.
The violence of the Saatchi Collection - his shedding of artists and eras as a snake abandons an exhausted skin - is itself an image of the history of Britain since the 1970s. As a nation, we have abandoned, buried, scorned history as brutally as Saatchi changes his taste; we are as cut off from pre-Thatcher Britain as the new Saatchi Gallery is from the collection he had in 1984, or 1989. Perhaps the appeal of this art for us is precisely that it mirrors our distance from the past - our having become, and still at the same time longing to become, contemporary.
Strip away all the myths, pull off layer after layer of obfuscation, penetrate the penumbra of Saatchi power and you find ... what? Someone who is perhaps stranger than anyone even thinks he is. Not Kurtz, certainly - but perhaps Jay Gatsby, a romantic of the modern, in desperate pursuit of some always-vanishing dream. There really is a singlemindness to Saatchi's collecting, despite - perhaps because of - all the sales and the convulsions and the jettisoned history. There is no overall logic to the range of artists he has loved and got bored with, but there is an overriding obsession with the contemporary, with this moment.
I can't imagine having his resources as a collector and never (even at 59) succumbing to the desire to own, say, a nice 18th-century painting. Saatchi, it seems, can't imagine wanting to collect anything but the newest generation. It must be exhausting to live in the present, to really, always and truly, be contemporary.
· The Saatchi Gallery, London SE1, opens on April 17. Details: 0207 823 2363.
