Princes William and Harry are to give readings at a memorial service for their mother, Diana, Princess of Wales, on the 10th anniversary of her death.
Princess Diana was killed in a car crash in Paris in 1997
Her sister, Lady Sarah McCorquodale, will also read at Friday's service.
Among 500 expected guests are more than 30 royals, including the Duchess of Cornwall, celebrities such as Sir Elton John, and Prime Minister Gordon Brown.
The hour-long service, in the Guards' Chapel in London's Wellington Barracks, will begin at midday on Friday.
Both William and Harry have been closely involved in organising the service, along with Earl Spencer, Lady McCorquodale and Lady Jane Fellowes.
Diana's musical tastes will be reflected, with some of her favourite classical music, by composers Rachmaninov and Mozart, being included.
Four hymns will be sung, concluding with her favourite, I vow to thee, my country.
The service, conducted by Rev Patrick Irwin, will also include two prayers written by Archbishop of Canterbury Rowan Williams.
An address will be given by the Bishop of London, the Rt Rev Dr Richard Chartres.
More than 30 members of the royal family have been invited to the service, headed by the Queen.
About 100 other family members have been invited, along with all of the bridesmaids and page boys from her 1981 wedding.
Former members of the princess's staff and over 110 representatives of charities and organisations with which she was associated are also on the guest list.
Prime Minister Gordon Brown and former prime ministers Sir John Major and Tony Blair have also been invited.
Sir Elton John, Sir Cliff Richard, Mario Testino and Lord Attenborough will be some of the other notable figures.
Princess Diana died, aged 36, along with her companion Dodi Al Fayed, 42, and chauffeur Henri Paul, when the Mercedes they were in crashed in the Pont de l'Alma tunnel in Paris on 31 August 1997.