A display of the late princess's gowns - including three never previously exhibited in the UK - will from March mark the reopening of the unoccupied part of the palace after a ?12?million refurbishment.
The centrepiece will be the low-cut black gown that heralded Diana's arrival as a global fashion icon, worn for a charity recital in the City in March 1981, 13 days after her engagement to Prince Charles.
Her fianc? told her black was only for those in mourning, but the dress, by David and Elizabeth Emanuel, who went on to design Diana's wedding gown, sent photographers into a frenzy.
"I was quite big-chested then and they all got frightfully excited," the princess recalled years later.
The dress, one of five to go on display, was recalled by royal watchers last night when they saw Kate's gown at a military awards ceremony.
Like Diana and the Emanuels, the duchess chose a dress from the fashion house which designed her wedding gown - Alexander McQueen.
The other Diana dresses never displayed before are a fuchsia and purple silk sari style by Catherine Walker, worn to dinner with the King of Thailand in 1988, and a black-and-white cocktail dress by Bellville Sassoon Lorcan Mullany worn to a series of gala performances from 1989.
A Catherine Walker ivory dress from Mario Testino's Vanity Fair photoshoot in 1997, shortly before Diana's death, and a black Versace dress worn to the 1995 Apollo 13 premiere complete the display.
Deirdre Murphy, curator at Kensington Palace, said the black Emanuel dress "starts off the story. Diana promoted British designers very well, something that carries on with members of the royal family today."