Why Princess Beatrice Secretly Opted for a 'Very Private, Intimate and Romantic' Wedding

Princess Beatrice and Edoardo Mapelli Mozzi pulled off something few couples ever do — a surprise royal wedding.

After the couple had to cancel their planned nuptials on May 29 due to the ongoing coronavirus pandemic, they quietly married in Windsor on Friday morning. About 20 close friends and family — including Beatrice's grandmother, Queen Elizabeth, 94 — attended the small ceremony at All Saint's Chapel in Windsor Great Park, a short drive from the castle.

"It was very private, intimate and romantic," a source tells PEOPLE.

Why did the couple choose July 17? It all came down to a very special guest.

"It was all about the Queen's schedule," the source says. "The Queen was the guest of honor, and it was very important that she was there."

The insider says there was no mandatory COVID-19 testing for wedding guests, but all attendees have been carefully practicing social distancing.

"It was planned for some time, and everyone had to be extremely cautious leading up to the big day because the Queen was in attendance. They had to make sure everyone who was attending was in perfect health," the source says.

With the marriage, the 31-year-old daughter of Prince Andrew and Sarah Ferguson also becomes stepmother to Edoardo's young son, born in 2016, whom he shares with his former girlfriend Dara Huang, an architect and designer. The little boy was at the ceremony and had a role in the big day.

"He is very much part of their life," Beatrice’s friend previously told PEOPLE. "Beatrice has embraced the child as part of her life from the outset."

Unlike Kate Middleton, Meghan Markle and younger sister Princess Eugenie's royal weddings, Princess Beatrice's nuptials were always set to be a "low-key" affair, which is what the couple wanted, a source previously told PEOPLE. Although they had planned to wed at St. James's Palace in London with a reception to follow at the Queen's gardens at Buckingham Palace, there were no plans for a horse-drawn carriage ride, for example.

The source says Princess Beatrice and Edoardo are having a "small party to celebrate" on Friday after the ceremony, and they're planning a honeymoon next month.

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Fergie recently told Royal Central that her daughter is "the happiest I have ever seen her in my life" despite having to change her wedding plans.

"She and Edo have a great love for each other and passion for life," the mother of the bride added. "For them to be getting married fills my heart with joy."