When art collector Charles Saatchi wants something, he knows how to set about getting it. Gallerists and curators are full of stories about the way he walks into an exhibition, fixes on the single best work of art on show and rushes towards it - in the words of one acquaintance, "like a heat-seeking missile".
Those who have seen him in action say that when he likes a piece of art, he will do everything he can to have it for himself. For Saatchi, worth a rumoured £135 million ($265 million), the price is irrelevant.
"He doesn't care whether it's worth £100 or £100 million," says a friend. It's all about the impact of the work when it is in front of him. When he wants something, he will pay on the day for it. More than that, he will have a truck waiting outside the door. It's a kid in a sweet shop and he just wants it now."
But what happens when he doesn't get what he wants? It's a question that many were asking after photographs emerged of Saatchi, 70, sitting at an outside table of his favourite restaurant, Scott's in Mayfair, central London, with a hand around the throat of his 53-year-old wife, television chef Nigella Lawson.
In some respects, it was difficult to know what to make of the pictures: there was no context for them and no sense, either, of what might go on within their relationship. The next day, Saatchi dismissed the incident as "a playful tiff" and later accepted a police caution because, in his words: "I thought it was better than the alternative of this hanging over all of us for months." And yet to others, the photographs were deeply disturbing. They seemed to suggest a silent power play, an act of borderline aggression. A few days later his wife was seen emerging from her sister's flat without her wedding ring and this week moved her belongings out of their home, including her cookbooks and the blender.
Around London, at private views and exhibition openings, there has been a discernible sense of shock and mystification.
"Everyone's really trying to grapple with them [the photographs]," says one gallery director. "You can't, from outside, interpret what's going on. I've never seen anyone so besotted as Charles is by Nigella. There's something magical about the way they found each other."
Tracey Emin, to whom Saatchi has been a generous patron, insisted that the couple "are in love ... I honestly believe that those people who are wasting their time speculating have never been in love".
Support came, too, from a more unlikely quarter. Kay Saatchi, the art tycoon's former wife, admitted that while her ex-husband "had his faults, I never experienced him to be physically abusive. He may be hard work, but I feel he is being treated unfairly."
Those in his social circle talk enthusiastically about Saatchi's qualities - his sense of humour, his fondness for shaggy dog stories that leave dinner guests in hysterics and his ability to make you feel like you are the most fascinating person in any room. He is said to be charming - interesting and interested - and transparent in his dealings. His employees tend to work for him for a long time and remain loyal.
Is there a darker side? One acquaintance says Saatchi has a form of "attention deficit disorder" that leads to impatience. He has been known to walk out of cinemas, prompted either by disgust or boredom. Writing in the Independent , journalist John Walsh recalled a mildly disquieting incident when he ran into Saatchi in HMV. Walsh's 14-year-old son, Max, was in the process of buying some CDs when Saatchi "turned his gaze upon a stranger, like a cobra eyeing its quaking prey" and proceeded to denounce Max's choice of an Elvis Costello album, apparently saying: "Why d'you want to go back to the old days? Absolutely not."
It would be fair to assume that Saatchi has never questioned his own taste. His certainty of touch has made him one of the most powerful forces in contemporary art. Saatchi is the man who bought Damien Hirst's formaldehyde installations of dead cows and sharks. He paid £150,000 for Tracey Emin's unmade bed when she was still a relative unknown.
When part of his private collection was shown at the Royal Academy (RA) in 1997 as Sensation, it blazed the trail for a new generation of young British artists including Marc Quinn, Sarah Lucas and Gillian Wearing.
According to Norman Rosenthal, then the RA's head of exhibitions, Saatchi is "a decisive figure in the history of British art of his time".
In the late 1990s and 2000s, Saatchi's golden aura was such that he could make an artist's reputation simply by visiting their degree show in his preferred garb of dark suit and crumpled white shirt.
He became a familiar sight around London, haring around in a black cab, clutching a copy of Time Out magazine in one hand and going to every exhibition in obscure parts of town. He was obsessed with seeking out the new, the exciting, the bold. "He doesn't care about the catalogue notes or the art historical context," says a colleague. "He just knows what he likes."
Saatchi was born in Iraq in 1943. Four years later, he and his brothers were brought to Britain after his parents fled persecution. They relocated to north London and his father bought two textile mills, building a thriving business. Charles went to a local school and then to the London College of Communication, before getting a job as a copywriter and discovering a genius for dreaming up swift, eye-catching images to convey a central message.
In 1970, he and his younger brother Maurice set up Saatchi & Saatchi, which grew to be the largest ad agency in the world. Its clients included British Airways, Silk Cut and the Conservative Party. When Saatchi & Saatchi developed the slogan "Labour Isn't Working" in 1978, above a picture of a long dole queue, it was credited with helping the Tories sweep to power in 1979.
In reality, the 100-strong queue was composed of 20 young Conservatives, with several photos superimposed on each other. It was a salutary lesson in the power of a manipulated image to make the necessary impact.
In 1995, the brothers were ousted in a boardroom coup and set up on their own as M&C Saatchi. Along the way, Charles had married Doris Lockhart, an American-born copywriter and art enthusiast with whom he started to collect his first works. After their divorce in 1990, Saatchi focused on a new wave of British artists, helped by his second wife, Kay Hartenstein, with whom he had a daughter, Phoebe.
Their 10-year marriage ended in divorce in August 2001, with Kay citing "unreasonable behaviour" and later characterising him as "a man of crushes - cars, clothes, artists".
He married Lawson in 2003, two years after the death of her first husband, journalist John Diamond, from throat cancer. Saatchi and her late husband had been close friends and many mutual acquaintances were delighted when the couple found happiness with each other. Until this week, they lived with her two teenage children in a seven-bedroom property in Chelsea, filled with works from his private collection.
But Saatchi's success has not left him without his critics. There is an argument that his buying power and consumerist approach towards art have distorted market values. Artist Peter Blake called Saatchi "a malign influence" because of his ability to build up some artists "and leave others as victims".
A few years ago, Hirst turned against his former mentor, accusing him of "only recognising art with his wallet". The two of them were later reconciled.
Having reached 70, there is a very real sense that Saatchi is no longer the dominant art figure he once was. When he was asked, as part of a 2009 book entitled My Name is Charles Saatchi and I Am an Artoholic, whether Sensation was his high point, Saatchi replied: "Well, it is never nice to be told your best days are behind you. But you're probably right." He has been expanding into Chinese and Middle Eastern art but he seems to lack some of his old elan. A guest who attended a Saatchi Gallery opening last week in Chelsea said: "To go to one of his openings no longer feels to be at the heart of art. It's very super rich and there are fewer smart young guns.
That powerful and discomforting picture is not easily forgotten. As Saatchi knows only too well, a single image can wield immense power.
Born: Baghdad,1943, the second of four sons to wealthy Iraqi Jewish parents who fled persecution in 1947 and settled in north London.
Best of times: His reputation as a collector and patron peaked in 1997 when part of his collection was shown at the Royal Academy as the exhibition Sensation which consolidated the career of several young British artists, including Damien Hirst and Tracey Emin.
Worst of times: Being photographed with a hand around the throat of his wife, Nigella Lawson.
What he says: "Women are all a little deranged, but why Nigella would wish to be with me is beyond human understanding. My bleating gratitude perhaps; surely a most effective aphrodisiac."