The religious service, exactly 10 years after her death in a Paris car crash, has triggered fresh recriminations against Charles' second wife. And the media have closely watched to see who's invited to the ceremony, who's not coming and who wasn't asked.
Emotions have quieted; there has been no repetition of the vast carpet of flowers laid outside Diana's palace by grieving Britons. But memories of the glamorous "people's princess" hold their grip on the public, remembrances of a woman who touched hearts, who suffered, who died.
A prayer written for the memorial service by the archbishop of Canterbury, Rowan Williams, gives thanks "for all the memories of her that we treasure still."
"Her vulnerability and her willingness to reach out to the excluded and forgotten touched us all; her generosity gave hope and joy to many. May she rest in peace where sorrow and pain are banished," Williams wrote.
Queen Elizabeth II will head the list of guests at the service in the Guards' Chapel near Buckingham Palace.
Charles' wife, Camilla, Duchess of Cornwall, changed her mind about attending in the face of criticism from those who blame her for breaking up his marriage to Diana.
"On reflection I believe my attendance could divert attention from the purpose of the occasion, which is to focus on the life and service of Diana," the duchess said last weekend.
Media reports have described Camilla as being furious with Charles, and Charles as pointing to his sons as the instigators of the troublesome invitation to their stepmother, which she at first accepted.
Diana's former butler, Paul Burrell, who has written two gossipy books about his years in her service, wasn't invited. Nor was Patrick Jephson, the princess' former private secretary, who also wrote two books about her.
Princes William and Harry, who have accused Burrell of a "cold and overt betrayal" of their mother, were among organizers of the event. They visited the chapel Thursday to make final preparations for the service.
"I have respect for the decision taken by Princes William and Harry, and understand the position from their point of view," Burrell said, denying newspapers reports that he had harangued the princes' office about his exclusion.
Mohamed al Fayed, who accuses Prince Philip of masterminding a plot to kill Diana and his son Dodi Fayed, also wasn't on the guest list. He plans two minutes of silence at Harrods, his department store.
Philip plans to attend Friday's service, but the event is not listed on the diary of Princess Anne, who was known to have a strained relationship with her sister-in-law.
Sir Elton John was invited, but he won't reprise his reworking of "Candle in the Wind," which he performed at the funeral.
Prime Minister Gordon Brown and former Prime Minister John Major, who was in office when the royal marriage broke up, also were invited, as were more than 110 representatives of charities and other organizations Diana supported.
Former Prime Minister Tony Blair will attend. It was he, with his perfect political pitch, who coined the term "people's princess" on the morning of Diana's death. "She was the people's princess," Blair said, "and that is how she will stay, how she will remain in our hearts and our memories forever."
Diana's brother, Earl Spencer, was involved in planning the service but isn't listed as a speaker. At her funeral, he took a swipe at the royal family, pledging to the young princes that he would work to insure "that their souls are not simply immersed by duty and tradition but can sing openly."
Invitations have also gone to representatives of her charities, including the Landmine Survivors Network, Help the Aged, the Trust for Sick Children in Wales and the National Aids Trust.
The royal family had refrained from any public remembrance of the anniversary of the princess' death, leaving that to a few fans who gather each year outside her former home, Kensington Palace.
The marriage of "Shy Di" to Prince Charles was fundamental to her global fame, and an integral part of the legend.
All the bridesmaids and page boys who participated in the lavish wedding at St. Paul's Cathedral in 1981 have been invited to the memorial service. Other guests include Diana's 12 godchildren.
One of the hymns to be sung Friday, "I Vow to Thee My Country," was chosen by Diana for the wedding.
This year, however, William and Harry took the lead in organizing the memorial service, as well as a rock concert on Diana's birthday, July 1, which drew 70,000 paying fans.
Affirming Diana's continuing star power, two television channels plan live coverage of the service.
"I think that because Diana died young, at the age of 36, she joins James Dean, JFK, Elvis and John Lennon, all icons who died young," said Martyn Gregory, author of "Diana: The last days".
"And because she died young and in an accident, she and her memory is preserved as if an aspic -- forever."