Tracey Emin stands by My Bed as it goes on sale for £1.2m

Vincent van Gogh never had to stand in the glare of a hundred cameras acting as salesperson for the art he had created out of the depths of despair and suffering.

Van Gogh was dead before his works ever became famous or saleable. By the time his painting of his homely straw-covered kitchen chair was cherished as a symbolic self-portrait, Vincent had truly left the building.

But here is Tracey Emin posing for the cameras next to My Bed, a work that is, like Vincent's Chair, a self-portrait through objects. Where Van Gogh painted his empty chair, Emin in 1998 offered up her own bed as a work of art, its sheet stained like a profane Turin Shroud, surrounded by objects that might be offerings to the gods of bohemian romanticism: two empty bottles of Absolut vodka and one of Stolichnaya among the Marlboros, aspirin, condoms used and unused, tampons and plasters for blistered feet.

It says everything about our time that while in the 1880s Van Gogh created art of the soul in the obscurity of fields and lunatic asylums, the equivalent of his expressionist art today is an object of intense celebrity on sale at Christie's auction house. My Bed is the pearl in its upcoming auction of postwar and contemporary art on 1 and 2 July, and can be seen for the next few days exhibited in its St James's showroom in London, for all the world like the bed of the last Tsar or Queen Elizabeth I or whoever else's bed is valued at up to £1.2m. Even a portrait of Lucian Freud by Francis Bacon that Roald Dahl bought with the profits from Charlie and the Chocolate Factory gets second billing in the sale.

What is more, Emin is here to speak for her bed even though she will not get a penny from its auction. The seller is Charles Saatchi, who bought My Bed for £150,000 in 2000, but he's nowhere to be seen. Instead it's Emin joking with the photographers, picking up her belt out of the installation and pointing out, "That used to be my weight." It's set to a tiny waistline.

Talking to me later she returns to this. On the morning of the press view, she personally set up My Bed at Christie's, so she's intimately revisited every detail of it. "I'm twice the size I was, so I'm twice the person. I'm not on the pill any more because I've got no chance of getting pregnant. I'm not so wild any more. I made it 16 years ago: a lot happens to a person in their life. I'm 51 next week. Let's hope things have changed."

But was her life in 1998 really as chaotic and extreme as My Bed makes it look? It is a desperately romantic work, a portrait of the artist as a bohemian outlaw. The booze and relics of casual sex tell of a life on the edge. Was it really like that?

"It was worse than that. I was suffering with a broken heart at the time."

But she is also an artist with a lot of art in her head. My Bed is brilliantly staged. It is all real, she insists, the evidence of her life, but it is also arranged in a spectacularly effective way. I ask if she intended it to be similar to Van Gogh's painting of his empty chair.

"How about Van Gogh's Bed?"

Oh yeah... As she points out, "I went to art school for seven years."

In fact, the more I look at My Bed in the quiet after the photographers have rushed off, the deeper its artistic echoes resound. After examining the Polaroids, old newspaper, McDonalds Barbecue sauce pack, Duracell packaging, mirror, tissues and KY Jelly scattered around, I suddenly notice the way the not-so-white undersheet is partially tucked into the bed's frame so that swags of drapery hang down.

Suddenly I am seeing the bedsheets of Velázquez's Rokeby Venus and Manet's Olympia. And then it hits me. For centuries male artists have painted naked women reclining on beds. In Emin's feminist masterpiece, the nude has left the building. She has walked away and left her bed as the work of art – not a woman displayed as an object but a woman displaying her inner life and feelings through objects.

When I bring up Manet's Olympia with Emin I get the equivalent of "Well, duh!" for an answer. She is completely aware of the comparison. "It's a good historical reference."

In fact, the similarities go deep. When Manet's painting of a nude prostitute was shown at the Paris Salon in the 1850s it provoked hysterical protests and screams of derision and horror. Olympia was seen as utterly obscene, a scandalous encounter with base reality. 19th century audiences had no problem with nudes. It was the raw factuality of Manet's nude that caused such terror.

My Bed is a work of art that like Olympia has lived its life in public, in storms of anger and shock. When it was shown in the Turner prize exhibition in 1999 people queued up to see exactly how rancid the evidence of Emin's life really was. "In Japan they were shocked by my slippers" - they're old and manky - "but stole the condoms", she remembers. At the Turner it was a spectacle that changed the very nature of British art. Before My Bed, the art of the Young British Art generation she belongs to was controversial but not exactly a household word. After My Bed it became true popular culture and Emin herself has been a celebrity ever since. Not just an art world celebrity - a proper one.

No wonder she feels obliged to sit here by her bed, posing with it, speaking for it.

She confirms she will not make a penny from the sale. She just feels she has to look out for her bed.

"I really care about the bed. I love it. I stand by it. If I could have bought it and given it to the Tate, I would."

It's clear why Tracey Emin cares about this sale. A good price will doubtless increase her prices generally. But I get the impression this is not about money for her. Emin is driven to communicate. Fame probably means more to her than wealth. She's right to champion My Bed because as the years go by it looks more and more like the work she will be remembered for, the perfect embodiment of her confessional, diary-like art.

Can a bed be worth £1.2m? Can some tear-stained tissues? The paradox of art in our century is laid bare in its absolute extremes as I sit opposite Emin and glance at her bed exhibited like a royal relic in one of the world's most potent auction houses. It is all clearly so absurd. How do you price it, is the KY Jelly worth more than the vodka or less? Is that how it all adds up?

And yet, this is so plainly and passionately and blatantly an impressive and moving work of art. Emin has the gift of being natural in the spotlight. She's her own real thing. My Bed too is utterly real. It is as simple as a photograph and as expressive as Van Gogh's chair … Or his bed. The sheets may be stained but they have a weird purity.

Artists have used many means to create self-portraits. Emin has used her bed and its surroundings. A lovely, simple idea. She agrees it is a self-portrait.

"A self-portrait from 1998. It's like a ghost: there's this presence of someone but they're just not there any more."

The cameras flash. The photographers shout her name. The woman who made the bed is here, and not here. We're none of us the same people we were. Perhaps, like a classic pop song, My Bed was always destined to get better with the years. It really is a ghost. An old photograph, which is yellowing with time - the newspaper on the floor looks ancient. Cigarette stubs and tears. It's turning into a golden oldie.

So how much is a broken heart worth?