London —  

Private letters from the late Princess Diana to actor Terence Stamp, who died last year, are going on sale, revealing the depth of their friendship and touching on topics such as royal duties, mental health and their social lives.

Written between July and December 1991, the correspondence details the princess’ friendship with the British star. The letters are part of an auction of Stamp’s estate at Bonhams in London.

In one letter written in September 1991, Diana thanks Stamp for lunch, saying “the champagne was excellent and I reckon that there aren’t many bottles like that around.”

The front of the light-hearted card reads: “Why did God invent Sex?…” Before continuing inside “…so that married people do something together at least twice a year!”

One of the handwritten letters from Princess Diana to Terence Stamp due to go on sale at Bonhams in London
One of the handwritten letters from Princess Diana to Terence Stamp due to go on sale at Bonhams in London
Courtesy Bonhams

On December 7, 1991, Diana asked Stamp to lunch, saying: “I haven’t seen a Cancerian for far too long and cannot cope with Christmas without a meeting.” The message is written on a postcard of a bare breast with a face drawn on it. The writing on the front of the postcard reads: “All The Breast from London.”

Not all of the letters are in such light spirits. Diana wrote to Stamp on October 17, 1991, saying: “You are so kind to me and I’m touched to the core by your understanding of my job/role and what comes with it.”

She continues: “Not many people would take the time and trouble to delve into such a complex situation… Three cheers for Prozac, not the American variety I hasten to add.”

Prozac, the brand name for the drug fluoxetine, is used to treat depression and other mental health conditions, such as obsessive compulsive disorder (OCD) and bulimia, according to the UK’s National Health Service (NHS).

Among the letters for sale are personal notes written on Kensington Palace headed paper, as well as Christmas cards.
Among the letters for sale are personal notes written on Kensington Palace headed paper, as well as Christmas cards.
Courtesy Bonhams

The letters, sold separately, are expected to sell for between £500 ($670) and £2,000 ($2,700) apiece, and are part of a wider auction of Stamp’s estate at Bonhams starting on Monday.

Stamp, who died last year, was “a defining figure of London in the swinging sixties, emblematic of a certain style and charm,” Claire Tole-Moir, head of popular culture at Bonhams, said in a press release.