8 Secrets from Princess Diana and Prince Charles' Royal Wedding — 40 Years Ago Today

Designer Elizabeth Emanuel recalls that the young bride-to-be morphed as the weeks elapsed before her July 29, 1981 wedding to Prince Charles, losing a notable amount of the weight she had when she first walked in.

"Most brides do lose weight," Emanuel previously told PEOPLE. "So we weren't that worried when she did. She ended up with a 23-inch waist from a 26- to 27- inch.

Years later, Diana spoke publicly about her struggle with bulimia during the time of her wedding.

"The bulimia started the week after we got engaged (and would take nearly a decade to overcome)," Diana said in Andrew Morton's book, Diana: Her True Story — in Her Own Words.

"My husband [Prince Charles] put his hand on my waistline and said: 'Oh, a bit chubby here, aren't we?' and that triggered off something in me. And the Camilla thing," she said, referencing Charles' relationship with Camilla Parker Bowles.

"I didn't like myself, I was ashamed I couldn't cope with the pressures," Diana continued. "I had bulimia for a number of years, and that's like a secret disease. It's a repetitive pattern which is very destructive. It was my escape mechanism."

Diana walked down the aisle of St. Paul's Cathedral wearing one of her favorite scents: Quelques Fleurs. But according to her makeup artist, it almost wore her.

Barbara Daly famously revealed that the young princess, then 20 years old, accidentally spilled some perfume on her dress as she tried to put some on her wrists after getting dressed in the world famous bridal gown.

According to Daly, she told her to simply hold that spot on her dress as she was walking to make it seem like she was lifting the front of her dress so she didn't step on it. She was even spotted trying to cover the spot where the perfume spilled with her hand as she approached the altar.

Diana knew her dress' 25-foot-long train was difficult to handle, and let her young bridesmaids know it. Prince Charles' goddaughter, India Hicks, recalled to Harper's Bazaar when she and Diana's niece Sarah Armstrong-Jones were in charge of guiding it down the aisle.

Hicks said that as Diana entered the catherdral, she told the girls, "Do your best."

Hicks wrote, "We knew what that meant: If we pulled too much, straightening the material, her tiara and veil would slip. But if we didn't pull enough, the effect of the train would be lost."

Florist David Longman told Express that after Queen Elizabeth lost the flowers during her own wedding, she started the tradition of having two identical bouquets made to prevent a similar mishap.

"We made two bouquets. The first one had to be delivered at 8 o'clock to Buckingham Palace. We had a police escort motorcyclist who took us all through the city to the Palace," said Longman about Diana and Charles' wedding. "Then we came back, and by that time they had finished the second bouquet and back we went again."

Nerves got the best of Princess Diana while she was saying her vows. She accidentally referred to her groom as "Philip Charles" rather than "Charles Philip."

(But to be fair, his full name is Prince Charles Philip Arthur George. With so many names to remember, anyone would slip up!)

Although it wasn't visible in photographs, there was a hidden good luck charm in Diana's dress: a 18-carat gold horseshoe trinket studded with white diamonds.

"[The dress] was the fulfillment of her princess fantasy," wrote biographer Tina Brown, according to Vanity Fair. "She was insistent in her demand for its puffy sleeves and floating silk, its twenty-five-foot taffeta train, its nipped waist, and its antique lace embroidered with pearls and sequins."

In case of poor weather, Diana's dress designer made a parasol featuring the same lace as the dress as well as hand-embroidered pearls and sequins.

However, the skies were clear for the big day.

"It was probably a good thing. It was made of such light material that it certainly wasn't waterproof," Elizabeth Emanuel told the Daily Mail. "It wouldn't have done her much good!"

Despite Prince Charles and Camilla Parker Bowles' dating history, she still made the royal wedding's guest list — likely due to her husband Andrew Parker Bowles' role as the Commanding Officer of the Household Cavalry Mounted Regiment.

According to the biography Prince Charles: The Passions and Paradoxes of an Improbable Life, Charles felt pressured into his marriage to Diana and was still torn abut his love for the then-married Camilla — and even cried over it the night before his nuptials.