The scene outside Kate Middleton's flat in Chelsea yesterday morning was a predictable one. At 6am, dozens of tenacious journalists - TV crews and photographers - jostled with one another for position. What they wanted was a picture or clip of Prince William's girlfriend on her 25th birthday, leaving for work. And hours later, those unspectacular pictures were splashed across newspapers and websites all over the world.
Unpleasant, you might think, for an amiable girl such as Middleton. Prince William certainly does. He begged for the paparazzi to "stop harassing her". Stop the paparazzi? Impossible, surely. But William found an unlikely ally in Les Hinton, the executive chairman of News International, who announced a self-imposed ban on "paparazzi images" of Middleton in all the group's publications: The Sun, the News of the World, The Times, The Sunday Times, and thelondonpaper. The group, for whose red-top titles paparazzi pictures have been like oxygen, no longer wished to be part of the "media circus" outside her door.
News International, it seemed, had decided to be merciful. It was surprising, then, that on the day of the announcement, The Times featured a full-length picture of Middleton on its front page. Of course, The Times would contend that the picture, which was taken by an Associated Press photographer, could hardly be described as a "paparazzi image". Indeed, its two-page story - "Royal lawyers demand privacy crackdown" - details the legal measures Miss Middleton's lawyers are willing to use to protect their client's privacy.
But the front-page picture showed Middleton, looking less than happy, walking towards the camera. Is that a paparazzi image? It does not look like a portrait worked out by prior agreement. Then again, it was shot by a photographer from a reputable news agency, and was also taken in a public place. The main story on pages six and seven of the newspaper, meanwhile, was adorned by another full-length picture of Middleton and her royal boyfriend stepping into a car to the flash of paparazzi lenses. The same questions apply.
So what are "paparazzi images"? And who are these nefarious photographers lumped together under that seamy title of "the paparazzi"? News International was no help. When asked to expand on its definition of "paparazzi images" a spokesman said the company had decided to "carry out a ban on paparazzi images as they are understood in the generic sense - as generally understood by everyone".
The trouble is, not everyone understands. Is it the destination that defines the picture's status? Does it make any difference if I am looking at an unsolicited photograph of Drew Barrymore in Heat, or in Vanity Fair? Or is it the origin of the photograph that counts? Is it a paparazzi shot only if taken by a freelancer? Or do pictures taken by staff photographers count? Or is it about the chase? For every photographer who takes a punch from Chris Martin, there's one who's making a tidy sum with a pre-arranged "chance encounter" between star and snapper.
The term "paparazzo" was popularised in Federico Fellini's 1960 masterpiece La Dolce Vita. Fellini had remembered a school friend whose fidgety movements and constant energy had earned him the nickname "paparazzo" ("mosquito"), and the character of Signore Paparazzo, a news photographer, was born.
But the romantic associations of its inception have not endured. In the past 15 years, there can have been no species on earth more reviled than the paparazzi. Indeed, when Earl Spencer made a eulogy at the funeral of his sister, Diana, Princess of Wales, he talked about her wish to leave the country because of "the newspapers", and complained of a media plot to "bring her down".
"My explanation," said Spencer, "is that genuine goodness is threatening to those at the opposite end of the moral spectrum... [Diana] was, in the end, the most hunted person of the modern age."
There - in that ferocious and most public of accusations - was the popular definition of the paparazzi: they are, in the public's eye at least, hunters.
It was not always so. Dave Bennett, who styles himself as a "showbiz photographer", and stopped being an on-the-street hunter in 1994, remembers the 1980s, the golden early years of the British freelance celebrity photographer, as a more innocent time. "The [paparazzi] industry has grown so much in the past 15 years that there are now dangerous numbers of people out there," he says. "When I was doing the paparazzi stuff, it was pretty jovial. Because there were only a few of us, we'd get a coffee in Langan's or San Lorenzo. When the star came out of the restaurant, there'd be a bit of banter, they'd have their picture taken, and they'd get in the car. If Kate Middleton's coming out of Boujis tonight, there will be 30 guys there. No wonder she needs the police."
Why the surge in numbers? "Well, the numbers always swell when there's the expectation of a big announcement, as there is now," says Bennett. "What many people don't know is that when you see a big crowd of photographers outside Kate Middleton's door, some of them are Fleet Street's finest. Their papers send them down there so that they don't have to pay for agency pictures.
"Generally, the industry has grown because the marketplace demands it. And because of the agencies. In the past few years, freelancers have relied on the agencies to sell their wares, and the agencies have seen the financial potential. They've employed their own staff photographers, too, and that's multiplied the numbers."
Bennett describes the life of a modern-day paparazzo as being "all about the chase and the money".
"These guys aren't interested in photography," he says. "In my day, most paparazzi had wanted to be on Fleet Street, but had been forced to do the paparazzi stuff because they didn't get an opportunity. It's just not like that any more. Anyone can do it. The streets are very rough now. And I hear that in LA a lot of the guys who are doing this are what they call gangbangers. That will probably head here too."
PR Mark Borkowski says there has been an exponential increase in "bounty hunters".
"The number of old-school paparazzi, those who have a good relationship with PRs and their clients, is very small indeed. Now we have people who seek a quarry. These are people with no photographic skills. It's all about getting the picture. Digital technology has changed things for people. Now everyone can be a photographer. Last year, Noel Edmonds had his picture taken by guys who had been hiding up a tree in camouflage in mid-winter for days."
What digital technology has also created, is the so-called Waparazzi - the camera-phone-toting Joes who take pictures of celebrities and send them to agencies. For most celebrities, this is wonderful news. Never have there been more opportunities to have one's knickerlessness displayed in so many formats. But for retiring types - such as Middleton - it is a precarious environment in which to protect one's privacy.
The relationship between the paparazzi and the privacy laws has always been a tricky one. Unlike in Germany, where photographers must ask permission from their subjects to take shots, British law is fuzzy. And the Press Complaints Commission's code on invasion of privacy, admits the organisation's assistant director, Stephen Abell, contains some grey areas. While it is "unacceptable to photograph individuals in a private place without their consent", the definition of a "private place" is moot. Just ask Britney Spears.
"A private place," says Abell, "is public or private property where there is a reasonable expectation of privacy. So, the commission has considered public places where one would have a reasonable expectation of privacy to be a church, inside a restaurant, or one's place of work." But not on the street?
"It depends on the circumstance. Issues can be raised over the conduct of the photographer. For instance, the code talks about "persistent pursuit" being forbidden - so following someone is a contravention of the code."
Antony White QC, a specialist in privacy law at Matrix Chambers, says the devil is in the detail. "It's absolutely all about context," he says. One is not, for instance, fair game, as soon as one steps foot outside the house.
"If you're standing in the doorway, you're in the 'tidal zone' between private and public. Likewise if you're leaving the doctor's - even if you're leaving on to a public street. That might be called being 'in the aftermath of a private situation'. Parks and beaches are especially difficult, because they tend to contain both open spaces and secluded corners. Where one places oneself may have implications as to whether you consider yourself in public or in private."
Three of the most valuable news images of the past two years - Kate Moss taking cocaine; survivors finding their way out of Aldgate station on 7 July; and Saddam Hussein's execution - have been taken on mobile phones. But White is adamant that it doesn't matter whether you are a professional photographer or a bystander with a mobile phone camera. Everyone is subject to the same regulations.
"It all depends on the nature of the photograph and the context in which it is taken," White says. "And, critically, what you do with it."
It's what you do with it that counts. In the aftermath of Diana's death in 1997, a number of vituperative recriminations landed at the media's door. In this environment, some of the editors of Britain's national newspapers agreed a temporary armistice on using paparazzi images in their publications.
But the truce did not last. Before a year had passed, newspapers that had spoken out about the use of paparazzi images were back in the saddle. And they were there because they believed the paparazzi images made their newspapers more entertaining. They were probably correct.
So before we damn the paps to hell, it is worth reflecting that most of us today will consume one of their images. Early in 2006 I spent a day at Matrix Pictures, one of London's bigger paparazzi agencies, and two things struck me. The first was that, despite a certain swagger surrounding the major photographers - Stephen Walters, for instance, described himself as one of those "nasty celebrity photographers who likes to catch celebs at exactly the wrong moment - most of the employees were un-demonic.
The second was that, as each of the pictures dropped on to the agency's screens, the editors were able to work out precisely how much each image was worth and where they would be able to place it. When Marco Deidda and Jon Bushell caught Elton John kissing a friend in a bookshop, the editors immediately said it would make two red-tops - and thus it came to pass.
The experience showed the industry as a highly evolved business where every celebrity had a market worth. And, as Bennett says, it's not about the quality. When the mobile phone footage of Kate Moss snorting cocaine hit the front page of the Sunday Mirror, its rival, The Daily Mail, surmised that it had paid £150,000 for the images.
So, everybody has the potential to become seriously rich at the touch of a button. The paparazzi only continue to exist because they happen to be the most committed, and the most ruthless at collecting the images. The number of publications that document every last kiss and pratfall of the world's VIPs have increased exponentially over the past decade. And the money available to photographers with an exclusive has only matched the public's appetite to see those pictures. When Darryn Lyons, an Australian photographer who set up London's biggest paparazzi agency, Big Pictures, boasted that he had "made" magazines such as Heat and Closer in the 1990s, he was only half-exaggerating. Supply met demand.
So, if you are appalled at the intrusion into an ordinary girl's life, think on this - you wanted to see those pictures. I have a neuron in my brain devoted to Kate Middleton, and, if you have picked up a British newspaper in the past week, so do you. A study, carried out in 2005 by neuroscientists at the University of California, Los Angeles, claimed that the human brain contains neurons reserved for individual celebrities. So, when the boffins showed their guinea pigs a picture of Halle Berry, one neuron lit up. We all have a Julia Roberts neuron, a Tom Cruise neuron, even a Jade Goody one.
And we all now have a Kate Middleton neuron. For the past few days, as pundits predicted her engagement to the future King of England, the British public have been subject to an avalanche of Middleton pictures. Even News International's publications will publish pictures of our Queen-to-be (though they broke their own rule last night when thelondonpaper published a paparazzi picture of her). So we have a part of our brain whose purpose is to be satisfied by a pretty brunette in a Topshop dress. And for that, we can blame the paparazzi, or, if we are really brave, ourselves.
Who's who in 'celebrity photography'?
* DARRYN LYONS
Australian-born founder of the Big Pictures agency, and the biggest player in the world of "snatched" celebrity pictures. His work fills the pages of celebrity magazines such as Heat and Closer, which, he claims, would not have existed without him.
* JAMES PELTEKIAN
Long-established freelance, whose current online gallery includes shots of Prince William. Specialises in parties and other events, at which he has once photographed Kate Middleton (with her permission). Says he never gatecrashes. Refuses to do pavement or snatched shots.
* DAVE HOGAN
Award-winning snapper who now works for Getty Images. Says that he's a celebrity photographer, not a paparazzo. Specialises in big celebrity shoots, such as Mariah Carey, and says he has no desire to photograph Big Brother winners.
* REX FEATURES
Agency whose best-known photographer is Richard Young (pictured right) does both standard showbiz photocalls - premieres, parties and the like - as well as more unofficial shots. Its website is currently offering photographs of actors Keeley Hawes and Matthew Macfadyen out shopping in London, seemingly unaware that they were being pictured.
Long-established, major British agency that specialises in fashion, music and "red-carpet" photography, as well as staged and studio shots of celebrities. Admits to undertaking a certain amount of paparazzi work.
* JASON FRASER
Considered king of the "set-up" pap shot, he is believed to have been used by many celebrities to get the photographs they are happy with in the media. Estimated to have made more than £1.5m from shots of the Princess of Wales kissing Dodi Fayed shortly before they died.
Established in 1999, Matrix has prospered in the boom in "informal" celebrity snapping, but, like Fraser, says it works closely with celebrities and their agents. Has taken decision not to doorstep Kate Middleton, but will shoot her when she appears in public places such as nightclubs.