For Diana's best friend Rosa Monckton, the greatest gift the Princess ever gave her was the key to her most treasured secret.
When Rosa gave birth to a stillborn baby girl in 1994, Diana made a surprising offer, suggesting Rosa might wish to bury her daughter in the gardens at Kensington Palace.
"What an extraordinary thing to do," Rosa told Melissa Doyle in an exclusive Sunday Night interview.
"We had a very, very moving ceremony and she gave me a key to the garden.
"She said 'you come in whenever you want, policemen at the gate will know'. I still have the key."
Rosa revealed that in her time of greatest need, Diana was the best friend anyone could wish for.
"She just completely understood. She understood what I was feeling, she understood what I had to do, she understood that I needed to rant and rage and cry and she gave me space to do all of those things and she carved her diary out so that she could come and see me," Rosa said
"She was amazing, I was very, very lucky to have her as a friend."
The following year, Rosa welcomed the arrival of her daughter, Domenica, who was born with Down syndrome.
Diana was the first person to visit Rosa and Domenica in hospital.
"She just gave me the biggest hug and picked Domenica up and said, 'I'm going to be her godmother. She's going to need all the help she can get'," Rosa said.
"She was a true friend."