When Federico Fellini coined the term 'paparazzo' in his film La Dolce Vita in 1960, he had spent years shadowing scandal sheet photographers, the people who provided, in his phrase, hedonism's 'worrying mirror'. In the wake of Hollywood's post-studio slump, American movie stars gathered in Cinecitta and rubbed shoulders on the Via Veneto with a corrupt European aristocracy. Rome in the late 1950s was, as Fellini put it, 'in a constant state of self-celebration, self-depiction, self-congratulation'.

The night Tazio Secchiaroli made the front page of Il Giorno for getting into a fi ght with the King of Egypt while attempting to take his picture, Fellini was with him in the swarm of snappers. A character was born. Paparazzo, the name of the boisterously invasive photographer who accompanies Marcello Mastroianni's hack in La Dolce Vita, is derived from a pejorative term for a very large mosquito.

In those days, style was born of necessity. The cameras used were old Rolleifl exes, with flashes that took an age to recharge. Photographers knew they would only get one chance, and that they had to come up close: they got their assistants to drive them around on Vespas so they could quickly swoop in for a shot.

No wonder celebrities looked shocked. The art of the paparazzo was part illustration, part circus act, as much a performance as the gathering of images. It was, Secchiaroli later remembered, 'only movement, action, a fast, instinctive thing'. 'We'll fight with flashes,' he declared. Soon, the art became so familiar that the battles had to be engineered. Secchiaroli learned that a straight shot of a star would sell for 3,000 lire, but one of a furious celebrity could fetch L200,000. There was nothing left but to provoke.

Secchiaroli's true heir was Ron Galella, who transposed many of his methods to New York. Galella's success came by scandals of his own making, and he is now best known for his photographs of Jackie Onassis, who fi led a lawsuit against him in 1972 . As a result, Galella was prevented from coming within 100 yards of her home, or within 50 yards of her or her children.

In his heyday, Galella seemed impossible to deter. He was hospitalised after being beaten by Richard Burton's bodyguards; he was spat on by Sean Penn; Marlon Brando broke his jaw, and as a result Brando's hand became infected, a symbolic effect upon which we need not dwell. Did this staunch Galella's outings? Of course not. He simply took the precaution, when chasing Brando, of wearing a football helmet.

Nevertheless Aristotle Onassis told Galella: 'You're a baby compared to the paparazzi in Europe.' In 1997, that seemed horrifically true. Though French courts ruled that the photographers who chased Princess Diana's car were not to blame for her death, the paparazzi's stunts would rarely seem so lighthearted again.

These days, many of the 'paparazzi' shots we see are set-ups. Everyone knows that the style - a stolen look, even a hand in front of the face - adds authenticity, and often celebrities will get their publicists to ring snappers and let them know that they can be seen, say, exiting Starbucks in Malibu with a soy frappuccino at 10.45. Paps live in fear that stars will, as they say, 'pull a Sarah Jessica Parker': that is, stand outside a hospital with their new baby for a universal photo op, thereby devaluing the shots to about $75 a piece when those photos could sell for - in the case of Brad and Angelina's baby - a rumoured million dollars.

Earlier this year, an anonymous paparazzo gave New York magazine a run down of current price tags that would make Tazio Secchiaroli tango in his grave. George Clooney alone: a few thousand bucks. Clooney with a woman: about $80,000. Tom Cruise and Katie Holmes together: 10 a penny. Holmes alone: $30,000 (cue headline: 'Where's Tom?'). A picture of the skeletal Nicole Richie with a cup of coffee will fetch almost nothing, but a picture of her eating? BINGO!