Princess Diana's Wedding Dress Designer Stored a Secret "Sister Dress" of One Famous Design at Hampton Court Palace

Elizabeth and David Emanuel catapulted to fashion stardom when they designed Princess Diana's royal wedding dress in 1981, but earlier the same year, they created another gown that put Lady Diana Spencer on the map. When Lady Diana Spencer made her first official appearance with her future husband, Prince Charles, she turned to the then-husband/wife team of the Emanuels to design a show-stopping evening dress, but it turns out a second black silk taffeta gown was created from the same material.

The shimmery ruffle-trimmed gown, known as the "Sister Dress," is now up for auction in the Julien's Auctions's Princess Diana's Style & A Royal Collection event. More than 300 pieces of royal fashion and memorabilia will be up for sale, including Diana's iconic "Caring Dress" and a rare letter she wrote to a footman at Buckingham Palace.

Elizabeth Emanuel attended a London press preview for the auction, which will be held in Beverly Hills on June 26, and she opened up to GB News about the second creation that Diana never wore. "I called it the Sister Dress because it came from the same bolt of fabric," she told the outlet. "Diana tried it on. We were considering this, and others—some black with gold sequins—but we kept coming back to this one."

While the "Sister Dress" is covered in sequins and features a v-neck trimmed with ruffles, Diana ultimately decided to go with a sexier, strapless version cut from the same black fabric.

The designer explained that she wanted to give Diana a more grown-up look than the "romantic, pastel, frothy dresses" she'd been wearing. "We thought this contrast would create a buzz, though we had no idea just how much," Emanuel said. "That black dress marked the transformation. She became a dazzling starlet in the making. From that moment on, she was a fashion icon."

Emanuel has kept the dress in storage at Hampton Court Palace with her archive of designs. "It’s in amazing condition because it’s never seen sunlight," she told GB News. "It’s exactly the same fabric as the original, made by the same seamstress, Nina. All the workmanship is there. From a historical perspective, it’s really important."

The "Sister Dress" is expected to fetch between $20,000 to $40,000 in the Julien's Auctions event, and a swatch of material and some rare sketches are also up for sale amongst the hundreds of other Diana items in the auction.

"These dresses are memories," Emanuel said. "They’re part of my life. But I thought it would be nice to bring them out of the darkness—especially for people who loved Diana and everything she represented."