Born on the Royal Estate at Sandringham, Diana became the people's princess.
Her death in a Paris car crash on August 31, 1997, at the age of 36, sent shockwaves around the world.
In Norfolk, as in London, floral tributes and poignant tributes told of a nation's grief.
The radiant Princess who had greeted wellwishers outside the little carrstone church at Sandringham with her young sons a few years earlier had gone.
Her smile and gentle compassion had become a beacon which had lit up lives, bringing hope to people many, many miles away from her childhood home in the pinewoods near King's Lynn.
She championed the disadvantaged, from those with Aids to the homeless, with a common touch which could bridge social divides.
On the day she died, prime minister Tony Blair dubbed said: 'People everywhere, not just here in Britain, kept faith with Princess Diana. They liked her, they loved her, they regarded her as one of the people.
'She was the People's Princess and that is how she will stay, how she will remain in our hearts and our memories for ever.'
In a magazine interview almost two decades later, Prince William said had her life not ended, his mother would have continued her work.
'I think she would have carried on, really getting stuck into various causes and making change,' he said.
'If you look at some of the issues she focused on, leprosy, Aids, landmines, she went for some tough areas. She would have carried on with that.'
William was 15 years old and Harry just 12 when Diana, her lover Dodi Fayed, 42, and their chauffeur Henri Paul were killed in the Pont de l'Alma tunnel.
Days later in London, the young princes walked behind the horse-drawn gun carriage transporting their mother's coffin through streets lined with mourners.
Both have spoken candidly about their mother for the first time in the run-up to the 20th anniversary of her death, describing the anguish they experienced and the grief they still feel.
Harry, interviewed for an ITV documentary about his mother, said: 'There's not a day that William and I don't wish that she was still around.
'And we wonder what kind of a mother she would be now, and what kind of a public role she would have, and what a difference she would be making.'
Diana was a woman of contradictions, labelled a clothes horse for the expensive designer outfits she wore, yet she used her public position to champion unfashionable causes from Aids awareness to banning landmines.
The simple gesture of shaking hands with an HIV-positive man – when many believed casual contact could spread the virus – challenged prejudices in the late 1980s.
And the year she died the Princess was famously pictured walking through an Angolan landmine field, being cleared by a charity, to highlight the impact buried munitions were having long after conflicts had ended.
But many will remember Diana for her clothes, worn to make a statement as well as express her style, and an exhibition of some of her famous outfits – Diana: Her Fashion Story – is being staged at Kensington Palace.
At the time of Diana's death, the Prince and Princess of Wales had been divorced for a year after the final stages of their marriage break-up had become public five years earlier.
Diana's marital troubles and personal issues had been laid bare in the 1992 Andrew Morton book Diana, Her True Story.
Three years later came more revelations when she told the BBC Panorama documentary that 'there were three of us in this marriage', in reference to Camilla Parker Bowles, now the Duchess of Cornwall, Prince Charles's wife.
In 1994, Charles had confessed to adultery in a TV interview with broadcaster Jonathan Dimbleby, but said it happened only after his marriage had 'irretrievably' broken down.
Diana's legacy is being taken forward by her sons, who have not only adopted some of her causes, from Aids awareness to supporting the homeless, but reflect to a degree her ability to connect with the vulnerable and disadvantaged.
So the Norfolk-born princess with an unorthodox approach to being a royal may help to keep the monarchy relevant in the 21st century.
In a BBC interview screened last night, William said only in the last few years has he come to appreciate what his mother gave the world.
'Now looking back over the last few years I've learnt to understand what it was that she gave the world and what she gave a lot of people,' he said.
'Back in the 90s there weren't many other public figures doing what she did, so she was this ray of light in a fairly grey world.'
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