The "Fashion Rules" exhibit presented by Kensington Palace includes gowns and outfits made famous by Queen Elizabeth II, the late Princess Margaret and Princess Diana – one of whose gowns is on loan from PEOPLE.
The princess's blue Jacques Azagury dress was bought for $26,450 at the Christie's of New York auction Diana held shortly before her tragic death in 1997.
With its "big shoulders, spangles and over-sized bow," as show curator Cassie Davies-Strodder described it, the dress is very much a of the '80s. Diana wore it on a visit to Florence, Italy, in 1985.
"It's not the most elegant, but it stirs people's nostalgia for the time," Davies-Strodder tells PEOPLE. "And she looked so happy wearing it. We were looking for dresses that were typical of the time and ones she wore and clearly loved."
Adds PEOPLE Managing Editor Larry Hackett: "PEOPLE was privileged to have Princess Diana grace our magazine's cover a record-breaking 57 times, more than any other public figure. We are thrilled that her exquisite blue and black sparkling Jacques Azagury dress is included."
Also on display are four others, including a glamorous red number from Bruce Oldfield, with whom she had a close working relationship. Diana wore it in Saudi Arabia, and Davies-Strodder says it was "ballsy and '80s, but also modest with its long sleeves."
Then there is a blue Murray Arbeid dress, which Diana wore several times, including for a 1986 dinner at Claridges for the president of Greece.
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It seems royal recycling is not new. "People often report that Kate wears outfits multiple times, but the Queen did so too, and Diana did with dresses like this one," says Davies-Strodder.
Before visitors to the exhibit reach the Diana room, they pass Princess Margaret's dresses. Margaret, who died at 71 in 2002, was known for her flamboyance and having friends across the pop culture world of the '60s and '70s.
One of the dresses was worn when she gave an award to ABBA. There are also a short day dress by Marc Bohan for Dior and a fur coat by Bohan, who was known for dressing Brigitte Bardot and Elizabeth Taylor.
"Princess Margaret was very much part of the chic London set," says Davies-Strodder. "It was very much 'what she wears is news' at the time."
Most eye-catching is a wonderful kaftan-style dress and turban she wore for an exotic fancy dress party on the Caribbean island of Mustique.
The show begins with a display of the Queen's outfits, mainly from the '50s and '60s by designers Norman Hartnell and Hardy Amies, showing off the fashionable hour-glass silhouettes. "The soft pale colors helped her stand out in a crowd, especially on black and white news footage of the time," Davies-Strodder says. "She kind of shines in crowds."
Missing from the exhibit: the outfits of the Duchess of Cambridge. "We felt it was too early and not the time to reflect on her style," Davies-Strodder says. "And it's not the time to ask her for things when she's starting a family. But we hope discussions will happen in the future."
Tickets – about $23 for adults, kids go free – are available at Hrp.org.uk.