For 40 years, Jackie Kennedy Onassis intrigued and captivated the world. Noreen Taylor meets Sarah Bradord, the biographer who has finally got to the heart of a legend

Sarah Bradford: author

I met Jacqueline Bouvier Kennedy Onassis in the late Eighties in the private carriage of a train carrying members of the Kennedy family back to London from the Welsh funeral of their friend Lord Harlech.

After a session singing old Irish ballads with the boisterous clan, Jackie invited me into her compartment and for the following few hours we talked our heads off.

The atmosphere was intimate, the conversation intense and wide-ranging, from current fashion to the potency of an Irish ancestry. She also marvelled at how the roles of women had changed in the intervening years, especially her perception of herself. To my amazement she even spoke frankly of her marriage to the President.

"Do you have to disappear?" she sighed as the train eventually pulled into Euston station. "We could go back to my hotel and have a neck massage." On the spur of the moment I declined, afraid perhaps the delicate spell might crumble.

About a year later I saw her again. I was gazing into a shop window in Park Avenue when I turned around and found her standing alongside. I smiled and was about to speak when the face behind the dark glasses froze. She turned swiftly on her heels and faded into the crowd. Gone. So quick and so efficient was her vanishing act, it must have been perfected through years of practice.

Had she remembered me from that eight-hour British Rail journey? I doubt it. What she had recognised was that a stranger was about to speak to her.

This was the elusive woman who built a social fortress to seal herself off from the ordinary world. So eager was she to preserve her privacy that in her will she charged her children to maintain it after her death.

In such circumstances, it is truly a measure of Sarah Bradford's skill as a biographer that she has managed to write such a compelling account of Jackie in her new book, America's Queen. She has accomplished what I have always assumed to be impossible, piercing the veil of secrecy to write an incisive, intelligent interpretation of a woman who defied anyone to know her.

Bradford, a striking, tall figure in beige, sits over a glass of wine in her favourite Kensington restaurant, relieved to have completed the book that has dominated four years of her life.

"So lovely to have some free time at last," she says in a voice that would not seem out of place in the London drawing rooms Jackie frequented.

During her researches Bradford travelled from Newport to New York, from the hunting country of Virginia to that hedonistic paradise of Skorpios, trawled through the archives of Washington and Boston libraries, infiltrated the salons of London, probing, reading and searching for clues.

Peering through the dusty windows of empty old Bouvier houses in East Hampton, she learned how those old monied families enjoyed languorous, romantic summers before the depression closed their palaces for ever. She spoke to journalists whose company the young Jacqueline Bouvier once enjoyed before distrust and dislike set in.

Such meticulous scrutiny paid off. One of the people who knew her, the famed US TV interviewer Barbara Walters, has praised the book as "the definitive biography of Jackie".

Having already written about powerful figures such as Disraeli, George VI and the Queen, what led Bradford to the woman whose power - apart from those few, ephemeral White House years - was largely spun from her role as the ultimate trophy wife?

"Because she intrigued me and I knew there was always more to her than that image of the fashion plate in a pill-box hat," says Bradford. "People say she didn't achieve anything, but I think she did. Along with her husband she turned Washington from a small town into one of the world's social centres. I think she made the Kennedy presidency, gave it a Sun King aspect.

"The restoration of the White House, which remains intact to this day, was largely due to her input. She searched out paintings and furniture that had been lost over the years, returning the historical soul to the house, and managed to do so with the help of her rich friends, without costing the taxpayer.

"She raised awareness in people about the importance of conserving historical sites such as Lafayette Square. Without her influence such places would no longer exist."

Shaking her head sympathetically at the slights suffered by her heroine, Sarah adds: "Jackie was no gold-digger. That reputation was largely undeserved." Indeed, meticulous examination of the Onassis papers reveals that, despite contrary advice, Jackie never sought a prenuptial agreement, believing it cheap and beneath her. "I won't barter myself," she told friends.

Sarah reveals: "Onassis did not treat her well. He was far too protective of his fortune to be generous. Certainly, during her marriages, she acted like a manic shopper. Perhaps it was her way of dealing with both her husbands' infidelities."

Like most of the women in her circle Jackie could never bask in the security of being the only woman in her husband's life. Both Kennedy and Onassis were serial philanderers, and far from being the stoical 18th century figure often depicted, she minded deeply.

"I don't know if I can stay with him," Jackie said of Kennedy, "he is so unfaithful." But the women whom Jackie seems most to have resented were those who remained close friends long after anything sexual between them was over.

She really loved Jack, no doubt about it. After she had complained about his flirtations, a friend said, "But surely it can't all be bleak?"

"'Oh no,' she countered quickly, 'it's sheer enchantment when he is around.'"

The hold that Jackie Kennedy Onassis retained on the world's imagination for all those years still baffles Sarah Bradford. "That, to me, is still the most difficult question of all. I never found anyone with a satisfactory answer. Possibly it lies with timing, and she caught her time brilliantly. The contrast between Jackie and predecessors like Bess Truman and Mamie Eisenhower was a profound one. Here was this beautiful, elegant young woman in the White House after years of those stout matronly figures.

"Also, I think the whole world was ready for the Sixties, for that brand of Kennedy glamour. Jackie was a great influence on women of my generation watching from the sidelines. I remember being beguiled by the handsome new president, comparing his family with the Macmillans who were then in Downing Street."

Now though, in her own middle age, how does Bradford feel about her subject?

"I decided I liked her. She was a woman with guts who endured the bleakest of times and survived. And the way she conducted herself at Kennedy's funeral, I think, gave America dignity, a sense of how to behave honourably in times of shock and deep stress.

"After the assassination there was a nervous breakdown which left her deeply shattered. Then, after Bobby Kennedy's assassination, the cracks grew deeper, and never really healed. How else could it have been?

"Her life wasn't particularly easy, either, especially during the early years when her parents divorced and her father's alcoholism ensured that she and her younger sister, Lee, remained the eternal outsiders."

Persuading Lee Bouvier Radziwill to talk about her sister immediately lifts the book shoulder high from the plethora of biographies purporting to reveal the "real" Jackie.

"It helped that I knew some people she did, as did my track record. I sent her a copy of Elizabeth, my biography of the Queen, and happily she agreed to meet me. She has never given an interview about her sister, so a four-hour lunch was quite a coup.

"A great deal of insight and understanding came from Lee. Details of their girlhood when they were close. Sadly though, by the end of Jackie's life, all sisterly closeness had been replaced by animosity.

"Can you imagine how hard it must have been for Lee who, throughout her life, was known as Jackie's sister? There was sadness when Jackie died naturally, but I suspect maybe a sense of relief too. She no longer had to lead her life in that shadow. Not that I got even a hint of bitterness from her, only regret.

"They disapproved of one another. Jackie felt Lee was a spendthrift and Lee thought Jackie a tight-wad. Also, the wounds caused by Jackie marrying Onassis, who had been Lee's lover, had never quite healed. Nor did it help when Lee's daughter, Christina, fell out with her mother and went to live with Jackie."

Joan Kennedy, who was close to Jackie, also helped with the biography. Ted Kennedy dithered and then finally said no. But Bradford persuaded many of Jackie's previously tight-lipped friends to open up. Antonia Fraser, for instance, told her of Jackie's close friendship with Edna O'Brien.

How did Sarah succeed where others have failed? She smiles, repeats her biographical track record, explaining that she planned the book like a military campaign. There was never anything as coarse as journalistic cold-calling.

She chose instead to bide her time, strengthening the interview chain, waiting for introductions from those whose trust she'd already won. Modestly, she agrees her own background must have helped considerably. Early networking amongst the smart set paid off.

Born in Bournemouth, from parents who came from a Singapore Army background, she was educated at St Mary's Convent, Shaftesbury, before winning a scholarship to Lady Margaret Hall, Oxford, where she read history and met her first husband Anthony Bradford.

"We were very young in 1959 when Ronald Tree invited us to Barbados and offered Anthony the job of personal secretary." Ronnie Tree, a rich Anglo-American, confidant of Churchill, and a junior minister in his war-time cabinet, was the original developer of the Sandy Lanes Hotel in Barbados.

The island became one of the watering holes of the rich, attracting sybarites like Onassis and Callas as well as personalities as diverse as the Duke of Roxburghe and John Steinbeck. "Barbados was part of my growing up experience," recalls Sarah. "I became aware of a bigger world, one where people wrote books, and quite different, as you can imagine, from Bournemouth.

"We went to New York a great deal and like everyone else I was fascinated by the Kennedys. Although I was very much on the sidelines I met people who knew them and who, years later, I was able to call on for help with the book."

The marriage ended in 1975 and Sarah, with her two children Edward and Annabella, eventually returned to London. She went to work in the manuscript department of Christie's and met her second husband, now an antiquarian bookseller. Then he was plain Mr Will Ward. Now he is the altogether grander Viscount Bangor who, along with Sarah, is a keen soccer fan.

She supports Liverpool while Will lives for Bolton. At matches, fans sitting close by noticeably moderate their coarse language after hearing Lady Bangor's dulcet tones urging her team to victory. Once a year the couple decamp from their elegant town house in Fulham to spend holidays at his ancestral pile, Castle Ward, in Co Down in Northern Ireland. Often described as the most beautiful house in Ireland, it nows belongs to the National Trust.

Back in the Seventies, Bradford admits, she had no confidence in herself as a writer. "Yet I loved to write. When I lived in Portugal for a while I became interested in those old port families, wrote an essay about them and sent it out to various agents. Only one replied, a marvellous woman, Juliet O'Hay, who commissioned a guide book to Portugal."

Sarah's book on port wine subsequently became a classic on the subject and fired her with the confidence needed to begin her career as a biographer. Her first, a study of Cesare Borgia, came out in 1976.

There would be more before her acclaimed biography of the Queen was published in 1996, furnishing her with a sense of how intimidated Her Majesty must have been by Jackie when the Kennedys were guests at a State dinner during their visit to London. Jackie, slim, would have been a formidable sight. "I believe both women were in awe of each other," says Bradford.

According to Bradford, Jackie found the Queen heavy going, although at the end of the evening Her Majesty seemed to warm up. "You like pictures," she said to Jackie. Then she marched her down a long gallery, stopping to point up at a Van Dyke, saying: "That's a good horse."

"They were two women in a cage," remarks Sarah. "The Queen acknowledged hers from the beginning, whereas Jackie never really got used to being in one."

Was she ever happy, ever at ease with her life? "Fleetingly, I believe. When she was swimming in Skorpios, when she was riding. Horses made her happy, but she was not a happy person."

By the end of her life Sarah believes Jackie had managed to reach a plateau of contentment. "She had an interesting job as a book editor, her children were in good shape, she had her hunting weekends in Virginia, her summers in Martha's Vineyard and Maurice Tempelsman, the comfortable companion and protector. Most important of all, for the first time in her life she was financially independent. The years of yearning had finally ended."