Old love letters. Not as many as he would have liked – an early, favourite ex demanded that all of hers be returned – but quite a few. Family photos. A washing machine. A Saab 900. Books and records. A lifetime’s worth of drawings and paintings, his own and other people’s. A sheepskin coat.

For a bloke with the usual run of earthly possessions, Michael Landy’s been having a strange time of it at work for the past few weeks. ‘We would all wear these blue boiler suits,’ says the 37-year-old Londoner. ‘I’d get up in the morning and go to work, but my goal was to destroy all my personal belongings. So it was a kind of a reversal, in a way.’

Landy is the progenitor of Breakdown, a three-year public art project that took place in a disused C&A shop at the Marble Arch end of Oxford Street, wherein all of his possessions – each record and CD, each pair of Patrick Cox shoes and Calvin Klein shorts, each item of kitchenware, each childhood photograph – was catalogued, sorted by type of material, and then systematically broken down into its component parts before being shredded, granulated or pulverised. After first being labelled and catalogued over the course of six months (“kind of documenting things, giving each thing a name, putting labels on, putting each object in a bag… it was very forensic”), his 7,009 catalogued possessions spent two weeks on display in bright yellow plastic bins, trundling round on conveyor belts, on display to passers by, awaiting execution.

Landy’s ‘operatives’ – his boilersuited assistants – were each in charge of dismantling a certain category of item (Clothing, Leisure, Artwork et cetera), and a Saab mechanic was brought in to dismantle his car. They had been instructed not to hack and chop and smash, but to take things apart with gentle precision: more euthanasia than execution, perhaps. “Basically, my operatives were told how to split everything down,” Landy explains. “They were given eight pages of procedural guidelines. But basically, they were told to do it in a loving way.”

The idea behind Breakdown, according to Landy, is to examine our relentless attachment to consumer culture, its wastefulness and ultimately, its vanity. Hence its location not in a gallery, but in a disused shop on a major shopping street, and hence the fact that absolutely nothing, including exhibition programmes or object fragments (which people, surprisingly, have been very keen to take away with them, like secular relics) is for sale.

“Having the piece of work on Oxford Street kind of gave it its context, really,” says Landy. “You’d have people going along, looking at shop windows in Dixons and stuff, and people obviously knew the building as a C&A. So people would come in, they would have been shopping, and they may have bought a similar kind of thing to something that might have been in one of my yellow trays. They’d talk about their own consuming habits, as well, to the operatives, or to the other people invigilating the exhibition.

“These trays full of all my objects, in their different states or whatever – recognisable things, or completely unrecognisable ’cos they’ve been broken down or shredded… My things are no different from anybody else’s. So people would still behave like shoppers, in a way. They’d be certain things that they liked, and things they didn’t. Like, children would always be aghast watching the teddy bears …getting it, or the Game Boy. But then, I’d always explain to them, There’ll always be a Game Boy 2 that’ll be far superior to Game Boy 1 anyway. You know.”

As a piece of public art, Breakdown seems to have struck a chord, not to say struck up a familiar, street-level relationship, with the public in a way that a more traditional public artwork could never hope to.

“Someone wrote a note,” Michael says, “and put it in a tray – I saw this note, and it just said, ‘Help me.’ People would write me things, or give me things, or people would come with presents. CDs. All sorts of different things. Some people wanted to swop something. And I said, No: can’t do that. But sometimes I’d give them a bit of granulated whatever. Or people would help themselves to some granules. So it was actually – there was kind of a lot of discourse, really. We also had the whole clergy in, as well... priests and nuns… Luckily, they didn’t see me get rid of the holy water,” he giggles. “People would try and steal things, as well. I thought I’d be really annoyed by that, but after I got my head round it, it was fine. And I’d almost want people to steal things, so that these things would go have a second life, somewhere else.”

For a man just out the other end of such a hardline project (Breakdown pulverised its last 45 and shredded its last sock about three weeks ago), Landy has the serene sense of humour of either an exceptionally wise Buddhist monk, or else a man for whom the full implications, and emotional fallout, of what he has done are still very much in the post. (This last he readily, cheerfully admits.)

“Sometimes it felt like a job,” he reflects. “You know, ’cos I had designed a very repetitive system. So sometimes it felt like a ‘process’ kind of production-line job, and then you’d see a photograph of an ex-girlfriend of mine, or whatever, and that would kick me back to reality. Sometimes I’d think it’s like my own funeral. I had quite a lot of publicity for it – the radio, the tv, the papers, and I suddenly had people popping into my life I hadn’t seen for twenty years. And then sometimes it felt like my own public execution.

“My mum came in on the last day, and by that time things were kind of really kind of building up into some sort of crescendo. And because we had had music on, it was a kind of jolly occasion, and… But when my mum came in, she started crying. That’s when it struck me that it was just like a public execution.” Landy giggles shortly. “’cos my mum’s crying. And I said Mum, look, I told her, you’ve just gotta go. You’ve got to leave the store, ’cos I can’t handle this. You’ve got to be really kind of level-headed. You’ve got to keep a level head, in and amongst everything, because otherwise… (pause)

“I conceptualised this idea three years ago. I made an artistic decision to do it, a conceptual decision to do this, so I had to see it through. The actualities are obviously different, the actual experience is something completely different.”

There were some items which remained on the conveyor belt until near the very end, things that he had particular sentimental attachment to.

“My dad’s sheepskin coat. That was the last thing that was actually taken apart. My dad came to see the exhibition, and I did offer him to take the coat back, for him to keep it, but um… People kind of thought that was a real test, that being on the conveyor belt for two weeks. Because it had been there for two weeks, they felt that somehow it was going to get a reprieve or something. So I think that was a kind of test, in a way. And it was like a drama: what things would be there the next day, what things had a stay of execution. It was very theatrical, actually.

“Once we actually got rid of my stereo, got rid of the turntable and all of that, suddenly there was a real hush, and there were only the sounds of kind of equipment - circular saws, tools and stuff. Before that we’d always had the music on, so it kind of gave the whole thing an upbeat kind of mood. But once that happened , it all turned – kind of morbid, in a way, I guess.”

It’s easy to see how destroying the symbols of everything that you are, might feel uncomfortably close to obliterating oneself, striking yourself from the record completely. What evidence is left on planet earth that you exist?

“Well obviously me,” Michael Landy says blithely, in a jaunty, I-got-plenty-of-nothin’ tone of voice. “Ahm. Myself. Ahhhmmmm.” He thinks. “I dunno. I think the hardest thing to destroy was, really, probably my artist’s archive.” (He’s referring to his career’s-worth of drawings, some of which were worth £6,000 each, all of which were in any case priceless and irreplaceable, presumably.) “Yeah. I think that’s what would upset artists the most, getting rid of the history of what I’ve done over the last twelve years…”

Are you being looked after financially?

“I live with my girlfriend. So I kind of borrow stuff off her.”

I bet she was really careful to separate the CDs before all this happened.

“Yeah,” he laughs shortly. “There were certain things, like photographs of each other, where it was kind of much more of a grey zone…”

Have you had any cynical reactions to Breakdown?

“Well I think the thing is,” says Landy, “no matter what one does, as far as trying to escape consumerism in a developed country, it’s inescapable. I mean, it wasn’t cynicism, but someone made a fair point in the Observer: they said I may be destroying my own personal belongings, but I’m kind of commodifying my name. And I thought that was a fair point to make. In certain regards I’m a much more well-known artist now than I was before I did the project. But I mean, I got five thousand pounds – it was a Times Newspapers / Artangel commission, they gave me a bog-standard fee that they give to all artists when they commission a public artwork. So I mean, the fee’s not about compensating me for my loss, because there’s no way they could do that anyway.”

People in our office, I tell him, were joking about how when friends go round to your house, you don’t let them in the garage. It takes Landy a moment to get this little joke.

“Oh! No, no, no, no, there was no point in cheating. ’cos if you’re going to do that, then it’s completely pointless to begin with.”

Three weeks later, Landy still has not made any purchases, any advances at all back into consumer culture. Will he ever?

“No. …Well, I have some clothes, and I buy food, ’cos if I don’t buy food I die, so … I think ultimately with some people Breakdown is kind of a conclusion, as if I should be dead now. But, you know, it’s an artwork. It purports to be a way of life, as well. But people have got to understand it finishes at some point.”

And what was the first thing you did after Breakdown finished?

“What did I do? Well, we all went for a ride on it. We sat in a yellow tray, each one of us, and we all went for a ride on the conveyor belts. Which took about ten minutes. Most of it’s at table level, but there’s some inclines and declines, and a high platform about twelve foot off the ground. So that was really fun. The next day, I stayed in bed, and then I and all my operatives got together, and we got completely plastered. We were up until about five or six in the morning. Dancing.”