By Chris Jones BBC News profiles unit

He is famed for nurturing Brit Art - including that melted blood head - and envied as the new partner of Nigella Lawson, but there's still an element of mystery about Charles Saatchi and his motives. There are no flies on Charles Saatchi, unlike the meals which featured in a food safety poster promotion for which he was the young copywriter.

His agency conceived the pregnant man

Saatchi's graphic description of the functions a household fly might perform on unattended morsels made people squirm, but conveyed the message.

As did his second campaign for the Health Education Council, designed to promote the use of contraceptives.

The picture of a pregnant man with the question "Would you be more careful if it was you that got pregnant?" was the idea of an assistant, but it was Saatchi's boldness that gave it the green light.

Saatchi has never been short of brainwaves from the time he and his younger brother, Maurice - now a Tory peer - set up their advertising agency in London in 1970.

Charles and Maurice deliver their message

The story, possibly embroidered, is that Charles hired a dozen strangers in the street to pose as advertising executives to persuade a potential major client that he was entering a busy office. It worked, and the Saatchis were on their way.

Charles Saatchi was born in Iraq in 1943. Four years later, he and Maurice were brought to Britain as their wealthy Jewish parents fled persecution.

Charles's formal education ended at 17, but when he formed a freelance consultancy a few years later he invited Maurice on board to utilise the analytical skills the younger Saatchi had gathered at the London School of Economics.

There are no hidden depths to me

Charles Saatchi

It was a 1978 poster, "Labour Isn't Working", which made Saatchi and Saatchi a household name, even though it was a fake.

The 100-strong queue of "unemployed" - suggesting it would be folly to re-elect Jim Callaghan's Labour government - was in fact composed of fewer than 20 Young Conservatives, with several photographs superimposed on each other.

It played a significant role in sending Margaret Thatcher to Downing Street.

Bloody mess: Saatchi's unfrozen art asset

By 1986, the brothers had made the agency the biggest in the world. But soon the bubble burst. Charles and Maurice were ousted in a boardroom coup, and set up a rival agency, M&C Saatchi, taking many of their clients with them.

By this time, Charles Saatchi had already established himself as a major collector of modern art. He and his first wife, Doris, an American-born art writer, staged impressive shows at the Saatchi Gallery in London's St John's Wood.

But after their divorce in 1990, Charles focused on a new wave of British artists - aided by his second bride, Kay Hartenstein.

[Saatchi] only recognises art with his wallet

Damien Hirst

It is Saatchi who is largely to blame/credit for making a star of Damien Hirst - his first acquisition was a glass box stocked with the decomposing head of a cow - and Tracey Emin, whose infamous unmade bed cost him �150,000.

Notoriously elusive, Charles Saatchi doesn't give interviews and seeks entertainment playing Scrabble or bridge with friends. "There's nothing complicated about me," he says.

Tracey's unmade bed

Now divorced from Saatchi, Kay Hartenstein recently characterised him as "a man of crushes - cars, clothes, artists". This remark was treated by some as a veiled warning to his partner, TV cook Nigella Lawson.

While Damien Hirst has called him a "shopaholic", Saatchi has described himself as "a gorger of the briefly new".

His acts of philanthropy, of bursaries at art schools and donations to the Arts Council, are well catalogued, but the artist Peter Blake says it must not be forgotten that he's a dealer as well as a collector.

"He has become a malign influence," says Blake, "by building up some artists and leaving others as victims."

This year, the British art world has been abuzz over the alleged personal rivalry between Saatchi and the curator of the Tate Modern, Sir Nicholas Serota. This animosity, it's said, is coming to a head with Saatchi's plan to show his wares just along the Thames at the former County Hall.

Master of all he surveys

Even more of a slight since it had once been supposed that one day the Tate Modern would get the bulk of his huge collection.

But one of the most remarkable Brit Art works, Self - a cast of the artist Marc Quinn's head made from his own frozen blood - is no more. The freezer in which it was stored at Saatchi's London home was reportedly switched off by builders.

In 1997, Saatchi's collection, "Sensation", whose exhibits included a portrait of Myra Hindley made from children's handprints, drew 300,000 people to the Royal Academy.

But Charles Saatchi says that while the Tate is now "the most fabulously successful museum in the world", his County Hall plan would be but "a small pimple".