Supporters tied bouquets to the gates of the palace

Flowers, photos and messages adorn the gates of her London home, as they did in 1997 after she and Dodi Fayed were killed in a car crash in Paris.

A Scotland Yard investigation into the crash is due to end later this year.

One visitor, 42-year-old Julia Cain, said: "We camped out overnight and we do it every year because we have to try to keep Diana's memory alive."

"As long as I've got breath in my body I'll be coming here," Ms Cain said.

Princess Diana was a wonderful, caring philanthropist Father Frank Gelli

Others said it was important to pay their respects to the "Queen of Hearts" in the year that her former husband, Prince Charles, married Camilla Parker Bowles.

John Chandler from Stratford, east London, said: "She was a lovely lady. It makes me feel sad but it was important to come because of the wedding."

The former curate of nearby St Mary Abbots Church, Father Frank Gelli, held his annual service in front of the palace gates.

Addressing a crowd of around 50 people, he said: "Princess Diana was a wonderful, caring philanthropist.

"She would come sometimes into the church and sit at the back and pray."

Father Gelli read a passage from the Gospel of St John and said special prayers for Diana and Dodi, as well as Princes William and Harry, who were spending the day privately.

Their father was on the Balmoral Estate in Scotland with the Duchess of Cornwall.