That's one leak which might have bemused those conservatives convinced that WikiLeaks was run by ultra-lefties. In the blogosphere, meanwhile, conspiracy theories abound that WikiLeaks is a CIA cyber-ops plot. Two years ago a Swiss bank in Zurich, Julius Baer, succeeded in temporarily closing down the website with a US District Court injunction after WikiLeaks published documents detailing how the bankers hid their wealthy clients' funds in offshore trusts (the banned documents reappeared on WikiLeaks ''mirror'' sites in places such as Belgium and Britain). The Australian government, too, has made noises about going after the website, after the Australian Communications and Media Authority's list of websites it may ban if the Rudd government goes ahead with its proposed internet censorship plan turned up on WikiLeaks last year. To say that the list of rattled people in high places around the world is growing because of WikiLeaks is an understatement. The fact that the website has no headquarters also means the conventional retaliatory measures - phones tapped, a raid by the authorities - are impossible. Intense interest in Julian Assange began well before the Baghdad video was released, and viewed 4.8 million times by the end of its first week. The former teenage hacker from Melbourne, whose mystique as an internet subversive, a resourceful loner with no fixed address, travelling constantly between countries with laptop and backpack, constitutes what you might call Assange's romantic appeal. But then there's the flip side: a man who believes in extreme transparency, but evades and obfuscates when it comes to talking about himself in the rare interviews that he gives. In the past, at least, these have hardly ever been face to face.

The secretiveness extends to those close to him. One woman who speaks to me on the condition of total anonymity lived in the same share house in Melbourne as Assange for a few months in early 2007, when WikiLeaks was in its incubation period. The house was the hub, and it was inhabited by computer geeks. There were beds everywhere, she says. There was even a bed in the kitchen. This woman slept on a mattress in Assange's room, and says she would sometimes wake up in the middle of the night to find him still glued to his computer. He frequently forget to eat or sleep, wrote mathematical formulas all over the walls and the doors, and used only red light bulbs in his room - on the basis that early man, if waking suddenly, would see only the gentle light of the campfire, and fall asleep again. He also went through a period of frustration that the human body has to be fed several times a day and experimented with eating just one meal every two days, in order to be more efficient. ''He was always extremely focused,'' she says. Well before meeting Assange, I'd thought how much he seemed like a character from Stieg Larsson's trilogy of blockbuster novels. One of Larsson's brilliant computer geniuses, taking on the world's wicked and powerful. Or a more youthful Mikael Blomkvist, with an Australian accent. Larsson died six years ago. But could the Swedish crime writer and Assange have met? Assange first visited Sweden in the 1990s - and WikiLeaks is hosted on a main server in Sweden, where the identities of confidential sources are protected by law.

This doesn't prove anything, of course - and WikiLeaks only moved its main server to Sweden two years ago, after the Julius Baer Bank tried to close down the website. Even so, I email Eva Gabrielsson, Larsson's widow, to ask if the two of them ever met Assange - explaining that he helped research a remarkable 1997 book, Underground, about the exploits of an extraordinary group of young Melbourne hackers, written by the Melbourne academic Suelette Dreyfus. The hackers all had monikers in the book: Assange is said to be the character Mendax. Assange convinced Dreyfus to release the book online, and according to one source I spoke to, there was great interest in the book in Sweden - and in China. ''About Julian Assange - well, why don't you ask him?'' Gabrielsson emails back. It isn't the most urgent question I have for Assange, who I meet in early May, the day after he slips back into Melbourne, his home town. He arrived on a flight from Europe, via the US. Or so I understand from the person acting as our inbetween. The same contact provides a Melbourne address, and instructions. ''Don't call a cab, find one on the street; turn off your mobile phone before you catch the cab and preferably, remove the batteries.'' And here he is - a tall, thin, pale figure with that remarkable white hair, looking very tired, and wearing creased, student-style dark clothes and boots, and backpack.

As we shake hands, he inclines his head slightly in a courtly, old world manner, at odds with his youthful, student-traveller looks. When I remark that there's a lot to ask him, he replies, ''That's all right - I'm not going to answer half of it.'' Is Assange his real name? Yes, he replies, then says it's the name in his passport. ''What's in a name?'' he then adds mysteriously, casting doubt on his first answer. At the time of writing, his passport status was apparently back to normal after immigration officials at Melbourne Airport said that his passport was going to be cancelled on the grounds that it was too tatty. It has been in a couple of rivers, Assange allows of the state of his passport. The first time, as he recalls, in December 2006, when he was crossing a swollen river during heavy rain in southern Tasmania, and was swept out to sea. He swam back in. ''My conclusion from that experience is that the universe doesn't give a damn about you, so it's a good thing you do.'' Why did he have his passport with him? He had everything he needed for three weeks of survival, he replies. He needed his passport for ID when he flew to Tasmania.

Doesn't he have a driver's licence? ''No comment.'' How true is the image of him as the enigmatic founder of WikiLeaks, constantly on the move, with no real place to call home? Is this really how he lives his life? ''Do I live my life as an enigmatic man?'' No - is it true you're constantly on the move? ''Pretty much true.''

Does he have one base he'd call home? ''I have four bases where I would go if I was sick, which is how I think about where home is.'' He has spent the best part of the past six months in Iceland, he says. And the next six months? ''It depends on which area of the world I'm needed most. We're an international organisation. We deal with international problems,'' he replies. Assange mentions four bases, but names only two. The one in Iceland and another in Kenya, where he has spent a lot of time, on and off, in the past couple of years. The Kroll report, released on WikiLeaks, reportedly swung the Kenyan presidential election in 2007.

When he's in the country, Assange lives in a compound in Nairobi with other foreigners, mainly members of NGOs such as Medecins Sans Frontieres. He originally went to Kenya in 2007 to give a lecture on WikiLeaks, when it was up and running. ''And ended up staying there,'' I suggest encouragingly. ''Mmmm.'' As a result of liking the place or … ''Well, it has got extraordinary opportunities for reforms. It had a revolution in the 1970s. It has only been a democracy since 2004 … I was introduced to senior people in journalism, in human rights very quickly.'' He has travelled to Siberia. Is there a third base there?

''No comment. I wish. The bear steak is good.'' Why did he go to Georgia? ''How do you know about that?'' I read it somewhere, I reply. It was a rumour. ''Ah, a rumour,'' he says. But he did go there? ''It's better that I don't comment on that, because Georgia is not such a big place.''

Living permanently in a state of exile, which can become addictive, means that you always have the sharp eye of the outsider, I suggest. ''The sense of perspective that interaction with multiple cultures gives you I find to be extremely valuable, because it allows you to see the structure of a country with greater clarity, and gives you a sense of mental independence,'' Assange replies. "You're not swept up in the trivialities of a nation. You can concentrate on the serious matters. Australia is a bit of a political wasteland. That's OK, as long as people recognise that. As long as people recognise that Australia is a suburb of a country called Anglo-Saxon.'' Could he ever live in one place again? A brief silence. ''I don't think so,'' he says finally. ''I don't see myself as a computer guru,'' he remarks at one point. ''I live a broad intellectual life. I'm good at a lot of things, except for spelling.''

At one point, thinking about some of the material leaked on WikiLeaks, I ask Assange how he defines national security. ''We don't,'' he says crisply. "We're not interested in that. We're interested in justice. We are a supranational organisation. So we're not interested in national security.'' How does he justify keeping his own life as private as possible, considering that he believes in extreme transparency? ''I don't justify it,'' he says, with just a hint of mischievousness. ''No one has sent us any official documents that were not published previously on me. Should they do so, and they meet our editorial criteria, we will publish them.'' Assange isn't paid a salary by WikiLeaks. He has investments, which he won't discuss. But during the 1990s he worked in computer security in Australia and overseas, devised software programmes - in 1997 he co-invented ''Rubberhose deniable encryption'', which he describes as a cryptographic system made for human rights workers wanting to protect sensitive data in the field - and also became a key figure in the free software movement. The whole point of free software, he comments, is to ''liberate it in all senses''. He adds: ''It' s part of the intellectual heritage of man. True intellectual heritage can't be bound up in intellectual property.''

Did being arrested, and later on finding himself in a courtroom, push him into a completely different reality that he had never thought about - and eventually in a direction that eventually saw him start thinking along the lines of a website like WikiLeaks, that would take on the world? ''That [experience] showed me how the justice system and bureaucracy worked, and did not work; what its abilities were and what its limitations were,'' he replies. ''And justice wasn't something that came out of the justice system. Justice was something that you bring to the justice system. And if you're lucky, or skilled, and you're in a country that isn't too corrupt, you can do that.'' In another life, Assange might have been a mathematician. He spent four years studying maths, mostly at Melbourne University - with stints at the Australian National University in Canberra - but never graduated, disenchanted, he says, with how many of his fellow students were conducting research for the US defence system. ''There are key cases which are just really f---ing obnoxious,'' he says. According to Assange, the US Defence Advance Research Project Agency was funding research which involved optimising the efficiency of a military bulldozer called the Grizzly Plough, which was used in the Iraqi desert during Operation Desert Storm during the 1991 Gulf War.

''It has a problem in that it gets damaged [from] the sand rolling up in front. The application of this bulldozer is to move at 60 kilometres an hour, sweeping barbed wire and so on before it, and get the sand and put it in the trenches where the [Iraqi] troops are, and bury them all alive and then roll over the top. So that's what Melbourne University's applied maths department was doing - studying how to improve the efficiency of the Grizzly Plough.'' Assange says he did a lot of soul-searching before he finally quit his studies in 2007. He had already started working with other people on a model of WikiLeaks by early 2006. There were people at the physics conference, he goes on, who were career physicists, ''and there was just something about their attire, and the way they moved their bodies, and of course the bags on their backs didn't help much either. I couldn't respect them as men''. His university experience didn't define his cynicism, though. Assange says that he's extremely cynical anyway. ''I painted every corner, floor, wall and ceiling in the 'room' I was in, black, until there was only one corner left. I mean intellectually,'' he adds. ''To me, it was the forced move [in chess], when you have to do something or you'll lose the game.'' So WikiLeaks was his forced move?

''That's the way it feels to me, yes. There were no other options left to me on the table.'' WikiLeaks, he says, has released more classified documents than the rest of the world press combined. ''That's not something I say as a way of saying how successful we are - rather, that shows you the parlous state of the rest of the media. How is it that a team of five people has managed to release to the public more suppressed information, at that level, than the rest of the world press combined? It's disgraceful.'' Where does Assange see WikiLeaks in 10 years? "It's not what I want the world to be. It's what I want the rest of the world to be," he replies. He would like to see all media develop their own forms of WikiLeaks. That would put his own website out of business, I point out.

''We have a proposal to [an American foundation] for a grant to just that,'' he replies, explaining that WikiLeaks could create systems for all media organisations. Loading A thought: has he ever met Rupert Murdoch? ''No.'' Nor has he met Stieg Larsson, Assange tells me.