On Monday, June 18, Prince William, Prince Charles, and Queen Elizabeth attended the Order of the Garter ceremony, but one very special person was missing from the annual event — Kate Middleton. So, where was she?

Since the Duchess of Cambridge gave birth to her third royal baby, Prince Louis, on April 23, she's technically been on maternity leave from royal events even though she still attended Prince Harry and Meghan Markle's wedding on May 19.

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This was a shakeup for royal fans, as the mom-of-three hasn't missed this special event in years. "The Duchess of Cambridge has attended nearly every Garter ceremony since 2011," Marlene Koenig, a British and European royalty expert, told HarpersBazaar.com. "She, as Catherine Middleton, and Harry were present in 2008 at William's first appearance as a Knight of the Garter." Last year, the event was canceled, but in 2017, she attended as a spectator.

Also absent from the royal gathering was Harry and Meghan, the new Duke and Duchess of Sussex. This is because Harry is not part of the order, and won't be until Charles is named King, so there's no need for Meghan to attend until he is. "The Duke of Sussex is not a Knight of the Garter and will probably not be invested until his father is King," Koenig added. "The Duchess of Sussex has never attended and will probably not attend until Harry is named."

Kensington Palace describes the day — which occurs every June — on their website. "The Queen and the Knights process in grand velvet robes, glistening insignia and plumed hats, is one of the most traditional ceremonies in the Queen's calendar. Every June, a grand procession of the knights takes place at Windsor Castle, accompanied by a marching band and Officers of the Order, all in grand ceremonial dress," the site reads.

The Queen — who is known as the "Sovereign of the Garter" — kicks off the special day by "formally investing any new Companions with the Order's insignia in the Throne Room of the Castle." Following that, there's a lunch that comes before a service at St. George's Chapel where new Companions are installed. "The Sovereign and other members of the Order then return to the Upper Ward of the castle in carriages and cars," the site concludes. We can't wait to see if Kate and Meghan attend the event next year!

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