Princess Eugenie was shocked in the best way when her boyfriend of seven years, Jack Brooksbank, proposed earlier this month.

Queen Elizabeth II's granddaughter (and eighth in line to the British throne) was joined by her fiancé for an interview with BBC 1's Matt Baker that will air tonight in the U.K. on the One Show.

During the interview, not only did Eugenie flash her gorgeous, pink engagement ring—a padparadscha sapphire surrounded by diamonds—she also dished the details behind the proposal.

The couple was visiting Nicaragua when they stopped beside a beautiful lake as the sun was setting.

"The lake was so beautiful," the Princess of York explained. "The light was just a special light I had never seen. I actually said, 'This is an incredible moment,' and then he popped the question, which was really surprising even though we've been together seven years."

Though Eugenie, 27, says she always knew they would one day get married, she had no idea Jack, 31, was about to propose.

"I was over the moon," she continued. "[It was a] complete surprise. But it was the perfect moment, we couldn't be happier. We knew it was going to end up this way."

Princess Eugenie, Jack Brooksbank, Engaged

Jonathan Brady/PA Images via Getty Images

Although Jack did get down on one knee, he proposed without a ring, knowing Eugenie would want to take part in designing it.

"I found a ring in a jewelers and then proposed to Eugenie without it," he explained. "[When we] came back, we designed the diamonds around this padparadscha sapphire...And what's amazing about it is that it changes color from every different angle that you look at it, which is what I think of Eugenie—that she changes color and is just so amazing."

Her grandmother, Queen Elizabeth, and grandfather, Prince Philip, were both informed of their engagement right away and are very pleased.

"Granny actually knew right at the beginning [of the engagement]," Eugenie explained. "She was very happy, as was my grandfather."

Meanwhile, Eugenie and Jack—the former manager of London club Mahiki—met during a ski trip in 2010.

They're set to wed at St George's Chapel, Windsor Castle—yes, the same venue as Prince Harry and Meghan Markle—in the fall.

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