Princess Diana wondered what her 30s had in store in a letter to a friend six years before her tragic death.
The Princess of Wales sent the fateful note to interior designer Dudley Poplak in 1991 to thank him for pictures he had drawn for her 30th birthday.
She told him: “I do wonder what the next 10 years will bring, the last 10 I have learnt a great deal in an interesting way.”
A year later, Princess Diana stunned the world by announcing her separation from Prince Charles.
Her death, aged 36, in a car crash followed in August 1997.
Diana’s letter to Poplak, on Kensington Palace-headed notepaper, is being sold at auction on July 30 alongside a separate note by her mother Frances Kydd.
Mimo Connell Lay, of David Lay Auctioneers, said: “These two items are from a retired dealer who is selling some of his most treasured items.
“The line where she contemplates the past decade during which she got married, became a mother and her marriage broke down, and what the future holds for her is very poignant.”
Poplak, who did work on Charles and Diana’s Gloucestershire home Highgrove House, died in 2005 aged 74.
The Diana letter is dated June 27, 1991, four days before her 30th birthday, but she confesses she had already opened the three “wonderful” drawings.
Of stepmum Raine Spencer, Diana jokes: “I am deeply touched to be given something that means such a lot to our family and that Raine hasn’t put under auction.”
Six years later she died with new-found love Dodi Fayed in the Paris tunnel smash.
