A "Lonely" Princess Diana Thanked One Unexpected Person for Their Friendship—and "Bowls of Cereal"—After Her Royal Wedding

Adjusting to life at Buckingham Palace wasn't easy for Princess Diana, who was just 20 when she married Prince Charles. But there was one person who helped support Lady Diana Spencer in the days leading up to her royal wedding—and a letter written by the royal bride just two days after her July 29, 1981 marriage is now up for auction.

Marie Claire recently attended a press preview for the upcoming Julien's Auctions Princess Diana's Style and a Royal Collection event, which will feature more than 300 pieces of royal fashion, letters, photos and other pieces of memorabilia up for sale. One such item is a letter dated July 31, 1981 to Mark Simpson, a footman at Buckingham Palace.

Martin Nolan, co-founder and executive director of Julien's Auctions, tells Marie Claire that the letter gives an insight into Diana's caring personality. "She was very lonely," he notes. "Remember, 19 years of age leaving behind her life where she was teaching kids, and sharing a flat in London with her friends and giggles and all that. And now she's in the palace being groomed to be the future Queen of England. That was her future."

Nolan adds that one palace footman, Mark Simpson, was a great source of comfort to the young royal bride-to-be. "Mark Simpson befriended her like she befriended him, and she wrote to him two days after her wedding to thank him for his friendship and for helping her through the lonely days at the palace."

The letter, which is estimated to sell for between $4,000 and $6,000, reads: "Dear Mark, I just wanted to thank you for all your kindness + patience you've showed towards me since I moved into B.P. My stay was made so much easier by your company as it was so terribly lonely + we had so many laughs for that I can't thank you enough. Do hope you were able to enjoy Wednesday + that you liked my dress? I'm off to Britannia tomorrow, what with all those men around. I will have to keep a watchful eye on Evelyn! The bad news is that I haven't eaten any cereal — sob. How am I going to cope without my bowls of cereal....[smiley face]."

She ended the letter, "A large thank you for being you—Much love, Diana."

As for the "bowls of cereal" Diana mentioned, Nolan tells Marie Claire, "I think he must have been trying to bring her bowls of cereal because she wasn't eating," noting that Diana "had dropped five sizes" from her initial wedding dress fitting to her final meeting with designers David and Elizabeth Emanuel.

"Elizabeth Emanuel had to alter the dress all the times and then the train had to be altered proportionately," the auction professional adds. Some of the swatches of lace that were cut from the dress are also up for sale in the Julien's Auctions event, which will take place on June 26 at the Peninsula in Beverly Hills, as well as online.

Other standout pieces from the auction include Diana's black Lady Dior bag, a hat worn on her honeymoon and the royal's "Caring Dress," which she frequently wore to children's hospitals. The colorful floral style is expected to break records, as Nolan told Marie Claire earlier this spring. The dress is estimated at $200,000 to $300,000, but could bring in more than $1 million, like her famous black sheep sweater and Jacques Azagury evening dress.