America's Queen: The Life of Jacqueline Kennedy Onassis
Sarah Bradford
Viking £20, pp690
Buy it at BOL

If Diana, Princess of Wales, had not died with Dodi al Fayed in that terrible Paris car crash, I wonder how she would be regarded today. What if she and Dodi had got married? Would we still accept her as the 'queen of our hearts' if she were now the daughter-in-law of the absurd proprietor of Harrods? As it is, the tragedy has made such questions redundant. Her status as a national icon - the beautiful, warm-hearted, exploited princess, the ideal queen who has been denied us - is likely to remain secure.

Tragedy made Jacqueline Kennedy an icon too - a far greater icon than Diana - but the tragedy in her case was the death of her husband, John Fitzgerald Kennedy. She had 30 more years to live after his assassination in Dallas in 1963, and during that time she horrified the world, and especially the Kennedy clan, by marrying the monstrous, bullying Greek shipping billionaire, Aristotle Onassis.

But even this failed to knock her off her pedestal, for she never forfeited the adulation of her fellow Americans. She remained fixed forever in their imaginations as the 'marble' widow at Kennedy's funeral, a grieving heroine who, as Sarah Bradford puts it, 'restored America's pride', exorcising the shame of the killing of the thirty-fifth President and becoming, in Frank Sinatra's words, 'America's queen'.

This was not entirely ordained by fate. Despite the strain of being married to a serial adulterer, Jackie Kennedy was a ruthless promoter of the Kennedy image while her husband was alive, and its ferocious custodian until her death in 1994. She regarded loyalty as the paramount virtue and anyone, even among her husband's greatest admirers, who went even the tiniest bit 'off message', as we would say now, would be brutally ejected from her circle, often never to be readmitted.

She was fully aware of her power as a national icon and once told the historian William Manchester, when she was trying to censor his official account of the assassination, that she was bound to win the argument because 'anybody who is against me will look like a rat unless I run off with Eddie Fisher'. (This was before she ran off with Onassis.)

Fiercely protective of her privacy, and commendably determined to bring up her two children, Caroline and John Jnr in as normal a way as possible in the most difficult circumstances, she was deeply suspicious of the press and extremely haughty towards it. Helen Thomas, a White House reporter, told Bradford that she 'treated the press like so many foreign invaders'. Once, when Jackie arrived back in Washington from Hyannis Port, the Kennedy home in Massachusetts, bearing a puppy given her as a birthday present by her father-in-law, Ambassador Joe Kennedy, the press sent her a note asking what she would feed it. She replied with one word: 'Reporters.'

But the press played her game, perhaps because it knew the public would never stomach the truth. Not until several years after JFK's death did the public hear anything about his addiction to sex ('I swear to you, and this is absolutely true, at this point it was chicer not to have slept with the President than to have slept with him,' said one New York society debutante), his dependence on amphetamines for his agonising back pain, or his father's links with the Chicago mafia.

If Jackie could tolerate her husband's infidelities and take part in the conspiracy to conceal them from the world, this may have been because her father, the handsome, drunken wastrel John Vernou Bouvier III - 'Black Jack', as he was called - was at least as bad. She adored him and was proud of his success with women, while he, in turn, warned her that 'all men are rats'.

She was conditioned by her family background to gravitate instinctively towards powerful, dominant men and, especially, very rich ones. She was obsessed with money, which she saw as the key to security and independence, and would never have married anyone less than a multi-millionaire. She was, Bradford frequently tells us, the ultimate American geisha.

This consummate myth-maker was brought up on a myth - that the Bouviers were descended from the highest nobility of France. Despite indisputable evidence that they were descended from lowly French shopkeepers, the family stuck to its story. Jackie may also have been influenced by a remark of her father-in-law during Jack's election campaign that 'It's not about what you are, it's about what people think you are'. Image was on JFK's mind to the end. His last words to his wife on that fateful car ride through Dallas were: 'Take off the glasses, Jackie.'

In this highly readable, if too long and sometimes repetitious, account of her life, Bradford brings out Jackie's appealing qualities - her intelligence, curiosity and sense of fun, as well as her selfless devotion to her children and her extraordinary courage. But the real Jackie remains concealed behind the protective shell with which she surrounded herself since childhood to keep an ugly and dangerous world at bay.

As First Lady, she was no Hillary Clinton. She had little interest in and no influence over policy. To the White House, she contributed nothing practical except the taste of a cultivated society woman in its hugely expensive refurbishment. But she invented and nurtured the Camelot myth that still enthrals the world, and that was hardly a small achievement.