Princess Diana helped to "save" the Royal Family and stop Britain from becoming a republic, according to Sir Richard Branson.
The English entrepreneur, who was a friend of Diana's, has said the 20th anniversary of her death should be treated as an opportunity to celebrate her legacy.
He explained: "She's had two magnificent kids who have done fantastic things and will continue to do great things. And I would say that actually has saved the Royal Family.
"There was a time when Britain could have easily become a republic, a few years before her death.
"But now the thought of that has gone completely and I think that's largely to due to her two wonderful children."
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Diana's death and extraordinary legacy
Sir Richard first met Diana when she stayed on Necker Island, his private island paradise, with a young Prince William and Prince Harry.
Their regular tennis matches were often a time when she would talk about the more difficult aspects of her life in the public eye.
He said: "We used to play tennis together - she won of course. We'd obviously talk afterwards, she'd had a lot of struggles, and particularly in the last two or three years of her life, she would open up about them.
"She put on a very strong face about it and just got on with her life."
Image:Diana had air passengers in stitches when she took control of the tannoy in a cockpit
Sir Richard also recalled Diana's sense of fun - and how she had "everybody in fits of laughter" during a Virgin Atlantic flight.
"She went into the cockpit with Prince William on her knee and she got on the loudspeaker to everybody in the plane and said 'if you look out to the left you will see granny's house' as we flew over Windsor Castle," he said.
Comedian Ruby Wax, who was also a friend of the Princess, recalls being totally star-struck the first time she met Diana.
She said: "As she shook my hand I went into a plie position, and I couldn't pull out. I froze, with my legs in the second position in ballet as we call it."
Image:Ruby Wax says she was 'star-struck' meeting Princess Diana for the first time
Wax has recently worked with Prince William and Prince Harry on their Heads Together campaign.
She believes that, like their mother, they are shining a light on causes that traditionally have been surrounded by stigma.
"Mental health has such bad implications, so I would rather that they're the representatives than someone who is on screen. These are clean, healthy, smart, sexy boys," Wax added.
Image:July 1962: A family album picture of Lady Diana Spencer at Park House, Sandringham, on her first birthday
Image:1968: Diana with her brother Charles, Lord Althorp (Earl Spencer)
Image:1970: Diana during a summer holiday at Itchenor, West Sussex
Image:1974: Diana with Souffle, a Shetland pony, at her mother's home in Scotland during the summer holidays
Image:Oct 1980: Diana alongside Camilla Parker-Bowles at Ludlow Races where Prince Charles was competing
Image:Oct 1980: Diana watches Prince Charles finish second in the club amateur riders handicap steeplechase at Ludlow racecourse
Image:Sept 1980: Diana, aged 19, at the kindergarten in St George's Square, Pimlico, London, where she worked as a teacher
Image:Nov 1980: Diana is pursued by the media near her London flat after being linked romantically with the Prince of Wales
Image:Nov 1980: Diana leaves her flat at Coleherne Court in Earl's Court
Image:Feb 1981: Charles and Diana announce their engagement
Image:July 1981: Earl Spencer accompanies his daughter at her wedding to the Prince of Wales at St Paul's Cathedral
Image:July 1981: The newly married Prince and Princess of Wales kiss on the balcony of Buckingham Palace after their wedding ceremony at St Paul's
Image:Aug 1981: Charles and Diana take a break during their country stroll along the banks of the River Dee, during a holiday at Balmoral Castle
Image:June 1982: The proud couple on the steps of the Lindo Wing at St Mary's Hospital with their son Prince William
Image:1983: Diana and Charles watch an official event during their first royal Australian tour
Image:Sept 1984: The Prince and Princess of Wales leave hospital with their new baby Prince Henry (Harry)
Image:April 1985: Diana and Charles meet with Pope John Paul II during a private audience a the Vatican
Image:July 1985: Diana and Charles stand with Bob Geldof in the Royal Box at Wembley Stadium at the start of the Live Aid Transatlantic Spectacular
Image:Nov 1985: Diana wears a Victor Edelstein gown as she dances at a White House dinner with John Travolta. The gown sold for $222,500 during an AIDS charity auction
Image:Nov 1985: US President Ronald Reagan and his wife Nancy welcome Princess Diana and Prince Charles at the White House
Image:July 1985: Diana laughs with Carolyn Herbert in the Royal box at Wimbledon before the men's singles semifinal between Jimmy Connors and Kevin Curren
Image:June 1986: Prince Charles and pop stars look on as Princess Diana cuts a cake to mark the tenth year of the Prince's Trust at a charity rock concert at Wembley
Image:Feb 1987: Charles watches Diana and The Duchess of York in the snow at Klosters in the Swiss Alps
Image:Aug 1987: Diana holds William, 6, and Harry, 3, as they pose during a photo session in Palma de Mallorca, Spain
Image:June 1988: Diana in the driving seat of the 'Striker' tank, getting instructions from Sgt Chris O'Byrne on Salisbury Plain
Image:Aug 1988: Prince Harry yawns as his mother holds him at Marivent Palace as guests of King Juan Carlos and Queen Sofia in Mallorca
Image:Sept 1989: Diana follows her sons Prince Harry, 5, and Prince William, 7, on Harry's first day at the Wetherby School in Notting Hill, west London
Image:Feb 1992: Diana sits alone in front of the Taj Mahal during a Royal tour of India
Image:Feb 1992: Diana, William, and Harry applaud during the Wales vs France Five Nations Cup match at Cardiff Arms Park
Image:April 1991: Diana meets an AIDS patient at the hospital of the Federal University of Rio de Janeiro in Brazil
Image:Feb 1992: Diana holds the hands of Mother Teresa at the Missionary Sisters of Charity residence in Rome
Image:Feb 1992: Charles kisses Diana after playing a game of polo with a Rajasthan team in Jaipur, India
Image:Jan 1993: Diana relaxes on the sand during a visit to the beach on the Caribbean Island of Nevis
Image:Jan 1993: Diana enjoys the splash of a wave during a morning swim on the Caribbean Island of Nevis
Image:March 1993: Diana gives a high five to Danny Walters, a 29-year-old student onlooker, after her visit to the Riverpoint hostel for women in Southwark, London
Image:Aug 1993: Diana ducks whilst descending a log flume water ride, Splash Mountain, at Walt Disney World in Florida. Prince Harry is shown front left
Image:Dec 1993: Diana , patron of the National AIDS Trust, chats with singer George Michael before the start of the Concert of Hope in London to mark World AIDS Day
Image:June 1994: Diana meets invited guests at the Serpentine gallery in Hyde Park
Image:July 1994: Diana and Harry talk with Flavio Briatore, team manager for the Benetton Ford F-1 before the start of the British Grand Prix at Silverstone
Image:Jan 1995: Diana attends an awards ceremony for the Council of fashion Designers of America, in New York
Image:May 1995: The Prince of Wales, Prince William, Princess Diana and Prince Harry attend a ceremony in Hyde Park to commemorate the 50th Anniversary of VE Day
Image:Aug 1995: Diana, Harry, William and Charles watch the parade march past as part of the commemorations of VJ Day in London
Image:Sept 1995: Diana attends the concert 'Luciano Pavarotti and friends together for the children of Bosnia' in Modena, Italy
Image:Feb 1996: Diana pulls on her head scarf as her friend Jemima Goldsmith does the same at the Shaukat Khanum Memorial Cancer Hospital in Lahore, Pakistan
Image:Jan 1997: Diana walks in a safety corridor of the landmine field in Huanbo, Angola, during a visit to help a Red Cross campaign outlaw landmines worldwide
Image:July 1997: Diana comforts pop star Elton John as he weeps at a memorial mass for Italian fashion king Gianni Versace in Milan
Image:Aug 1997: Diana comforts a woman during a visit to Sarajevo's Lion cemetery on one of her last engagements highlighting the suffering of landmine victims
Image:Aug 1997: Diana and Dodi al Fayed cruising in Saint Tropez, South France, just weeks before they were killed in a car crash in Paris
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On Wednesday, the Duke and Duchess of Cambridge and Prince Harry will meet representatives from some of the charities that their mother supported in the sunken garden at Kensington Palace.
This year the garden has been given a special white theme in memory of Diana, who often used to stop and talk to the gardeners working on the grounds.
Thursday marks the 20th anniversary of the day Diana died in a car accident in Paris. She was 36 years old.
:: Watch Sky News' documentary Diana: The People's Princess at 8pm tonight.