Princess Diana's waist shrunk down to 23 inches for her wedding to Prince Charles

Like any bride-to-be, Lady Diana Spencer wanted to make sure she would fit into her wedding dress – except the 19-year-old was tying the knot with Prince Charles, England’s future king.

Designer Elizabeth Emanuel, who created Princess Diana’s iconic wedding dress for her royal wedding on July 29, 1981, told People Magazine Sunday the then-19-year-old was eager to shed her “puppy fat” before walking down the aisle.

“Most brides do lose weight,” Emanuel told the magazine. “So we weren’t that worried when she did. She was looking fantastic. She ended up with a 23-inch waist from a 26-to 27-inch.

"She just walked more confidently. She just was suddenly growing up, you know? But I think she felt very good about how she looked.”

Emanuel recalled how she and her husband and designing partner at the time created the majestic gown in total secrecy for the shy schoolteacher.

Princess Diana on her wedding day.

Princess Diana on her wedding day. (Reuters)

“She was just lovely, really kind of easygoing,” said Emanuel about the future Princess Diana. “We never had any special instructions about how to make the wedding dress. That added a bit to the fun of it all, made it a bit of an adventure.”

The designing duo decided to make Diana’s bridal train as long as possible because “St. Paul’s Cathedral is a really big area to fill.”

On the big day, Diana casually wore jeans and watched TV while having her jewel-encrusted tiara added to her freshly done hair.

“She was incredibly together and wasn’t panicking,” recalled Emanuel. “But I was really worried about all things that could possibly go wrong. We’d taken smelling salts, glucose tablets — what if she feels faint? What if she passes out? Spills something down her skirt?

"I had this kind of horror that maybe the train would drop off. We sewed her into things, we pinned her into things.”

But when the big moment came, the dress easily cascaded out of the royal carriage as Diana took her place alongside her proud father John, 8th Earl Spencer.

Town & Country reported the ivory taffeta dress was embroidered with sequins, frilled lace and 10,000 pearls. The designers attached an 18-carat gold trinket studded with white diamonds, a symbol of good luck. The veil was 25 feet and the silk shoes were reportedly covered in 542 sequins and 132 pearls.

Emanuel even created an umbrella with matching pearls in case of rain. And while Diana accidentally spilled some Quelques Fleurs perfume on the dress, she managed to hide the stain during the ceremony.

“It’s always been about a butterfly emerging from a chrysalis,” said Emanuel. “And that is her story, really. She was emerging into a new world, a new life’s adventure.”

Diana and Charles officially divorced in 1996. Since the gown’s original unveiling in 1981, it has traveled all over the world for appearances.

People reported the dress was passed down to the couple’s two sons, Princes William and Harry, as reportedly requested on Diana’s will.

Diana passed away in 1997 at age 36 from a tragic car crash in Paris.