A new official biography of Princess Diana is being published to mark Tuesday's seventh anniversary of her death in a Paris car crash.
The princess's death provoked an unprecedented outpouring of grief
The Princess of Wales Memorial Fund hopes the book will refocus public attention on her humanitarian work.
Prince William and Prince Harry are said to be remembering their mother in private.
A small collection of flowers from the public has been left outside her former home, Kensington Palace, London.
A Historic Royal Palaces spokesman said: "A handful of bouquets and posies are there already but it's not as many as last year.
"Kensington Palace has noticed it's getting fewer and fewer every year."
The princess's former husband, Prince Charles, is said to be spending the day at Birkhall, on the Balmoral Estate in Scotland.
There were no plans for any commemorative ceremonies at the beleaguered Diana memorial fountain in Hyde Park, which has been beset by drainage and safety problems since its official opening in July.
A Royal Parks spokesman said: "We will have an area set aside if people want to put their flowers there.
"Most people will leave them at Kensington Palace. That's the tradition."
The princess, her lover Dodi Fayed and chauffeur Henri Paul died when their Mercedes car crashed in the Pont d'Alma tunnel in Paris after leaving the Ritz Hotel on 31 August, 1997.
Bodyguard Trevor Rees-Jones was the only person to survive.
The princess's death provoked an unprecedented outpouring of national grief, with hundreds of thousands gathering to mourn outside Kensington Palace, where they left a sea of floral tributes.
Thousands more later lined the
route of her funeral procession.
An inquest into the deaths began this year but was adjourned while Scotland Yard Commissioner investigated the accident, which has sparked a succession of conspiracy theories.
An earlier investigation concluded that Mr Paul had been drinking and was driving at high speed.
Mr Paul's parents contest the findings and have started legal action in a French court to clear their son's name.