Speaking on behalf of Slingo, Mr Burrell said the princess was often “lonely” and Mr Simpson offered to go and “cheer her up”.
He added: “So we used to go down and chat with her and she said to me one day, ‘you know what I’d really love? I’d love a Big Mac and fries and a strawberry milkshake, do you think you could make that happen?’.
“Mark and I went down to Victoria, way back all those years, McDonalds weren’t on every street corner then and there was one by the cathedral in Victoria.
“We got Big Macs and strawberry milkshakes, we took them back to the royal nursery and sat on the floor cross-legged with her and it was a party, a picnic in a palace.”
Mr Burrell joined Charles and Diana’s royal household at Highgrove in 1987 and remained her butler until her death in 1997.
Diana supposedly referred to him as “the only man she ever trusted” and he described himself as her “best friend”.
In January 2023 Mr Burrell revealed he was being treated for prostate cancer, leaving him in fear he is running out of time to tell Princes William and Harry important information about their mother.
READ MORE: The tragic history of the Dukes of Edinburgh
The former butler told The Mirror that Diana had revealed some of her deepest secrets to him and would want him to pass them on to the princes.
He said: “I know some of it isn’t pretty, but if I leave this place and go somewhere else they’ll never know. I think they should know.
“My illness has focused my attention on telling the boys things before it’s too late – telling them what they really should know.
“I think Diana would say to me, ‘Paul, you must make this a priority. You must go and see my boys’.”
Mr Burrell said that he wished to see William and Harry reconciled, as the royal brothers have become increasingly estranged since Harry’s move to the US.
He continued: “I spent many hours with Diana, during her happiest times as well as her darkest times.
“She confided in me and there are many things I have never spoken about, but now I feel the time is right.
“I think what I have to say could bring the boys back together, which Diana would have desperately wanted. I will only tell them the truth, that is all. I am not looking for anything in return.”
