A full 13 years before Princess Diana’s revenge dress stole the headlines in 1994, then Lady Diana Spencer made her newly engaged debut with her fiancé Prince Charles wearing another black dress that cemented her fashion icon status—a mantle she held until her far-too-soon death on August 31, 1997.

On March 9, 1981, Charles and Diana had just gotten engaged weeks prior; they’d ultimately be married just a few months later on July 29, 1981 at St. Paul’s Cathedral. For their first public event as an engaged couple—held at Goldsmiths Hall in London, a fundraising concert in support of The Royal Opera House—Diana wore a revealing black dress that The Daily Mail reported was “two sizes too small” for her first official engagement alongside her soon-to-be husband. Diana, then just 19 years old, wore a creation by the married couple David and Elizabeth Emanuel, who would go on to design her wedding dress that same year.

Diana’s strapless taffeta gown was created by the Emanuels after Diana visited their studio to request an outfit for a “posh” evening function, according to The Daily Mail. “After trying on a black silk taffeta bodice, which happened to be on display, it was clear the style complemented her blue eyes and blonde hair,” the outlet reported.

David—“concerned that the strapless silhouette revealed too much skin”—crafted a matching black wrap for the future royal to drape over her shoulders. “That evening, when we switched on the news, the limousine pulls out, out got Prince Charles and there was this girl, and I said, ‘That’s the girl! That’s her! That’s the one we’ve just done the frock for!’”

Previously known for wearing soft tulle and pastel hues, this bold look marked a shift towards a more sophisticated style for Diana, “marking the early signs of her evolution into a global fashion icon,” The Daily Mail reported.

Diana, though beautiful, “appeared uneasy,” the publication wrote, and she herself later described the event to her biographer Andrew Morton as a “horrendous occasion.” For the book that became Diana: Her True Story (released in 1992), Diana said she was anxious, revealing that “I didn’t know whether to go out of the door first. I didn't know whether your handbag should be in your left or right hand.”

“I was terrified, really—at the time everything was all over the place,” she continued. “I remember that evening so well. I was terrified—nearly sick.”

Also in attendance was experienced royal Princess Grace of Monaco—who, tragically, would die just one year later in a car accident, 15 years before Diana’s own fatal crash. Charles apparently criticized Diana for wearing the black dress as, when it comes to royals, the color is typically reserved for those in mourning. This critique only served to make Diana more self-conscious.

“I remember walking into my husband-to-be’s study, and him saying, ‘You’re not going in that dress, are you?’” Diana told Morton. “I replied, ‘Yes, I am.’ And he said, ‘It’s black! But only people in mourning wear black!’”

“I thought it was okay because girls my age wore this dress,” Diana continued. “I hadn’t appreciated that I was now seen as a royal lady.”

Of the gown, Elizabeth Emanuel later told Vogue, “It felt so different to anything she’d worn before. She looked so grown up, like a movie star, and she loved the idea of breaking the mold.”

Emanuel also told British Vogue that, when designing the gown, she and her husband “didn’t even consider whether the dress was right for the occasion—we just thought she looked fabulous.”

“We witnessed the birth of a fashion icon before our very eyes,” she added.