Princess Diana’s wedding gown is perhaps one of the most famous dresses in history, but there was actually an alternate dress made that she could have worn down the aisle. Designers Elizabeth and David Emmanuel have unveiled this dress for the first time amidst the hype of Prince William and Kate Middleton’s upcoming nuptials.

“At the time we wanted to make absolutely sure that the dress was a surprise,” Elizabeth Emmanuel told People. She created both gowns with her husband David. “Had the secret of the real dress got out it’s possible that Diana would actually have worn this one.” They also wanted a backup dress in case of a fashion emergency. “We wanted to make sure that we had something there; it was for our own peace of mind, really,” said Emmanuel. “We didn’t try it on Diana. We never even discussed it.”

[ Flashback photos: More images from Princess Diana’s wedding day ]

The original gown Diana wore was crafted out of 275 yards of silk taffeta, tulle, and netting, and was covered in antique lace and 10,000 hand-embroidered pearls and mother-of-pearl sequins. It featured a boned bodice and a staggering 25-foot silk train that followed her down the aisle of St. Paul’s Cathedral. The backup gown was also ivory silk taffeta with similar ruffles around the neck, but there was no lace. As Diana’s wedding date approached, the spare dress was never fully completed.

Kate Middleton has expressed that she wants her wedding dress to remain a surprise until her April 29 wedding, but Princess Diana’s dress designer was announced ahead of time. This created a lot of stress and chaos surrounding the designers, who enlisted two full-time security guards and even discarded unrelated bridal materials to throw off snooping journalists. So while the world speculates about which dress Middleton will wear, Emmanuel understands why everyone is keeping the design under wraps. “They’re keeping quiet on the designer this time, probably to avoid all the hassle that we had,” Emmanuel told People. “It was really difficult and we didn’t have to contend with cameras in phones etc like you have today. How do you keep something secret like that? I have no idea.”

With all the hype and fanfare still surrounding Diana’s wedding dress (it is currently on a world tour), would you believe there is yet a third gown in existence? Only this one wasn’t made for the princess—it was made for a wax figure! The silk taffeta replica of Diana’s wedding gown was on exhibit at Madame Tussaud’s waxworks museum following her wedding to Prince Charles in 1981. It lacked the fancy lace and had a train one-third the length. The museum auctioned off the replica for $175,000 in 2005 to an anonymous private buyer.

[ Photos: Royal wedding dresses through the years ]

Despite confusion, dress designers Elizabeth and David Emmanuel said the replica dress was made specifically for the museum and Diana never actually wore it. “Diana never tried the dress on, it was never a backup dress,” Elizabeth Emmanuel said at the time. Nevertheless, auctioneer Cooper Owen had said the dress was very important. “It’s a dress that Diana personally said she wanted the world to see. She asked that a replica be made.”

Want to see Diana’s real wedding dress in person? Head to Kansas City’s Union Station for the Diana exhibit from now until June 12 to see the dress displayed as part of a 150 piece personal collection of the late Princess.

See more photos of the backup wedding dress at Rex USA.

For the best of Yahoo!’s coverage, visit the royal wedding home page.

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