Princess Diana’s Secret Backup Wedding Dress Recreated by Designer Elizabeth Emanuel 43 Years Later (Exclusive)

Elizabeth Emanuel made her mark with Princess Diana’s wedding gown, but there was another version waiting in the wings…just in case.

As Lady Diana Spencer climbed the steps of St. Paul’s Cathedral in London on July 29, 1981, to marry Prince Charles, her majestic wedding dress with its 25-foot train brought a royal fairy tale to life. But unbeknownst to the 20-year-old bride and the millions watching on television, the designers behind the now-iconic gown had crafted a second, mystery dress as a precautionary measure for any unforeseen circumstances.

“I was a bit neurotic, and I thought, ‘What happens if somebody breaks in and steals the dress or something spills or there’s a fire or it gets stolen?’ ” Elizabeth Emanuel, who famously created Princess Diana’s wedding gown with former husband David, tells PEOPLE exclusively in this week’s issue. “So I thought, ‘I’m gonna make a backup dress.’ ”

Drawing inspiration from a pink gown that the Emanuels made for Diana to wear at a private ball a few days before her wedding, Elizabeth quietly got to work.

The spare dress differed greatly from the famous gown that Princess Diana wore on her big day, notably lacking a long train. The silk was white, “not the deep ivory that the royal wedding dress was made of” and the backup had “slim ones, more fitted to her arms” with frilly cuffs, Elizabeth says. Additionally, the intricate designs on the dress Diana wore were hand-embroidered by Elizabeth, whereas the fabric for the backup was ready-made.