Prince Charles married Lady Diana Spencer in the royal wedding of the century on July 29, 1981.After forgetting to kiss at the altar, the couple rectified the error on the Buckingham Palace balcony in front of 600,000 onlookers.Queen Elizabeth, Diana’s new mother-in-law, gave a piece of advice to Diana as they waved at the crowds below.

On July 29, 1981, 600,000 people gathered on the streets of London to catch a glimpse of Prince Charles and Princess Diana on their wedding day, BBC reported. After marrying at St. Paul’s Cathedral—and forgetting to kiss at the altar—the new Prince and Princess of Wales headed to Buckingham Palace, where they stepped out on the palace’s balcony and started a tradition that continues with royal weddings up to the present day.

On the balcony, Diana interacted with not just her husband Charles but also her mother-in-law Queen Elizabeth, who told Diana as they were waving to the crowds of people below them to “look” at all of the people who had “been there all day” to see her, per a lip reader speaking to The Daily Mail.

Princess Diana, Prince Charles, and Queen Elizabeth on the Buckingham Palace balcony.

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Per Brides, the lip reader also caught that Charles told Diana, “You look perfect.” After the two forgot to kiss at the altar, Charles apparently sought to rectify that error, asking Diana for her hand and saying, “Kissy.” It’s a tradition that’s been carried on by royal couples since—with Prince William and Kate Middleton even sneaking in two balcony kisses for good measure.

The night before the wedding, royal biographer Penny Junor wrote in her book The Duchess: The Untold Story that Charles sent Diana a secret letter and a gift to alleviate her understandable nerves. “The night before the wedding, which Diana spent at Clarence House with her sister Jane, he sent her a note along with a signet ring bearing the Prince of Wales feathers,” Junor wrote. The note read, according to Junor, “I’m so proud of you, and when you come up, I’ll be there at the altar for you tomorrow. Just look ‘em in the eye and knock ‘em dead.”

Princess Diana and Prince Charles kissing on their wedding day.

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Princess Diana and Prince Charles on July 29, 1981.

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Yet not every account of the night before Charles and Diana’s wedding was as positive. “One of the most shocking things that Diana told me was that the night before the wedding, Charles told her that he didn’t love her,” Diana’s astrologer Penny Thornton said in the ITV documentary The Diana Interview: Revenge of a Princess. “I think Charles didn’t want to go into the wedding on a false pretense. He wanted to square it with her, and it was devastating for Diana.”

Thornton added that Diana “didn’t want to go through with the wedding at that point—she thought about not attending the wedding.”

Though what was happening behind the scenes wasn’t necessarily the stuff fairytales are made of, the wedding itself surely was. It cost roughly $48 million—equivalent to $170 million today, per People—and 750 million viewers across 74 countries watched the royal wedding on television.

Princess Diana, Prince Charles, and Queen Elizabeth.

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Diana walked into the marriage with hope and optimism, she told Andrew Morton for his 1992 book Diana: Her True Story. “I remember being so in love with my husband that I couldn’t take my eyes off him,” she said. “I just absolutely thought I was the luckiest girl in the world. He was going to look after me.”

Ultimately, Charles and Diana separated in 1992 and divorced in 1996, almost one year exactly before Diana lost her life at age 36 as a result of a car accident in Paris on August 31, 1997.