Princess Diana’s feelings of “trepidation” ahead of her newly single life have been revealed in a letter written before her divorce from the former Prince of Wales.

In correspondence with the chairman of the Royal New Zealand Foundation for The Blind, the princess explained she was ending her role as patron of the charity due to “personal circumstances” involving her marriage.

The previously unpublished letter, dated July 15, 1996, will be auctioned by Julien’s Auctions and Turner Classic Movies in Beverly Hills next month.

It reads: “Although I am embarking upon the future with hope, I also do so with some trepidation since there are a number of matters which I shall need to resolve.”

During her marriage, the late princess held more than 100 patronages for charities and organisations around the world.

After her divorce, she resigned from most of the roles and relinquished all her military appointments.

According to Buckingham Palace, the princess remained a patron of the homeless charity Centrepoint, the English National Ballet, the Leprosy Mission and the National Aids Trust. She also remained president of Great Ormond Street children’s hospital and of the Royal Marsden Hospital.

Late princess ‘continues to captivate’

The letter continued: “It is for this reason that I am writing in order to resign my current role as patron with you.

“As I seek to reorganise my life, it will not be possible for me to provide you with the right level of commitment and I feel there may be someone else better suited to support you in all that you do.”

Outfits owned by Princess Diana will be auctioned as part of the Legends: Hollywood and Royalty sale, which features more than 1000 rare objects synonymous with famous cultural figures.

The headline pieces include three of her designer dresses, which have not been seen in public for more than 30 years.

The princess’s scarlet Bruce Oldfield gown, which she wore while attending the film premiere of Hot Shots! at London’s Odeon Leicester Square in November 1991, is expected to sell for the highest price of between US$200,000 to $400,000 (NZ$336,000 to NZ$672,000).

A Catherine Walker strapless gown, which the princess wore to a private function, is expected to fetch between NZ$101,000 and $134,000.

A black and jade short-sleeved gown by the same designer, which she wore to a gala dinner in Toronto, Canada, in 1986, is expected to sell for up to NZ$336,000.

Darren Julien, founder of the auction house, said: “We look forward to celebrating … the beloved people’s princess, one of the most photographed women in the world, who changed the monarchy forever and whose persona continues to captivate the public and Hollywood today through tributes and film and television works about her life.”