Gown worn by Diana, Princess of Wales, twice in 1985 is going to auction

A gown worn by Diana, Princess of Wales, twice in 1985 is going to auction this month.

It was first seen on the late royal at a party when another guest turned up wearing the same outfit.

But Diana, who became known as the People's Princess, simply laughed off what others might have seen as an embarrassing faux pas.

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The black and white gown, by British designer Murray Arbeid, is being sold at Sotheby's Fashion Icons sale in New York.

It is estimated to sell for $US80,000 - $120,000 (approx. $124,000 - 186,000).

Also going to auction at the same event is the iconic black sheep jumper worn by Lady Diana Spencer soon before she married Prince Charles.

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The Murray Arbeid gown was first seen on Diana in June 1985 when she attended Prince Edward's 21st birthday party.

The Midsummer Nights Ball was held at Windsor Castle and Natasha Fairweather was among the invited guests.

She ended up wearing the same gown as Diana that night and recalled the experience to Vogue in 2021.

"My sister was living in London and much more glamorous than me, so she had this incredible dress she bought in the sale," Fairweather told the publication.

When she realised she was in an identical dress to the Princess of Wales, Fairweather was unsure what to do.

So she decided to ask the Queen Mother, who was also there.

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"I met someone who said, 'Well, I know the Queen Mother a bit and she's very good on this sort of thing'," Fairweather said.

"We found her in the drawing room, and I explained my predicament. She was very nice to me and she said, 'That's absolutely fine; you stay and enjoy yourself.'"

Fairweather then decided to approach then-Prince Charles and Diana.

"When I noticed that Diana and Charles had gone to the dance floor, I went and danced very close to them so that they would notice. As I remember it, Charles pointed it out to her and she laughed; it certainly wasn't a big deal."

Princess Diana wore the gown for a second time in December that same year, at the Worshipful Company of Fanmakers Banquet at Mansion House.

That time, she accessorised with her sapphire brooch and pearl choker gifted by the Queen Mother on her wedding day, and her double-drop sapphire cluster earrings.

The gown is described by the auction house as a "black velvet, lightly boned, and strapless bodice" that "carries down just past the knees and opens into a white taffeta quasi-mermaid silhouette supported by layers of tulle petticoats".

Cynthia Houlton, Sotheby's Global Head of Fashion and Accessories, said the dress was uniquely Diana.

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"This was a gown that other people could purchase, but she chose to wear this gown again," Houlton told People.

"I think what's special about it is that most women who buy evening gowns wear them more than once, so there's this relatable situation where she wore a gown that you could buy retail.

"Someone else was wearing it [at the party], but she still liked the gown enough that she decided to wear it again.

"She did things that were often relatable, she wasn't just always doing things that only someone in her position could do.

"That's what makes this gown specifically special."

The gown and black sheep jumper will be auctioned online between August 31 and September 14.

In a separate sale from Septmber 6, held by Julien's Auctions, three of Princess Diana's gowns will be up for grabs in Los Angeles.

The dresses were created by two of the late royal's most-loved designers, Bruce Oldfield and Catherine Walker.