Meghan Markle has quickly adapted to royal tradition. She has perfected the royal curtsy, she's adopted sheer stockings into her wardrobe and she basically has her PhD in the "duchess slant." (Well, make that had.) The newly crowned Duchess of Sussex had a minor slip-up with royal posture protocol during Tuesday's party at the Buckingham Palace - and PEOPLE's Simon Perry captured the exact moment she realized it.
After expertly demonstrating the "duchess slant" at numerous royal events in the past, Meghan seemed to innocently forget the pose (at official engagements royal women are supposed to cross their legs at the ankles or put both legs off to the side to maintain poise and posture) when taking her seat beside Prince Harry and Queen Elizabeth at Buckingham Palace to celebrate a group of young leaders from across the world. At first she accidentally crossed her legs, but she quickly recovered, uncrossing her legs at the knee and slanting them to the side. See her "whoops" moment in the clip below.
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According to proper etiquette, which sister-in-law Kate Middleton also follows, royal women keep legs and knees together, although crossing at the ankle is fine, which Megan expertly demonstrated at her solo outing with the Queen earlier this month.
Myka Meier, royal etiquette expert and founder and director of Beaumont Etiquette, told PEOPLE earlier this year that "biggest etiquette mistakes a lady can make" is to cross her legs at the knee.
Meier, noted, women should sit with their knees and ankles together and should only cross their legs at the ankle if needed. "It's sophisticated, protects vulnerabilities and looks fabulous in photos," she shared with PEOPLE.
The "duchess slant" has been adopted at royal outings when a lady "has to sit for an extended amount of time while keeping poise and posture," Meier, explained. "It is the perfect pose for when a camera is shooting directly in front of you because by slightly slanting the knees to create a zig-zag effect when wearing a dress or skirt, your legs are angled so that the camera only shoots the sides of your legs and protects your modesty."
Meier also explained that the slant helps make your legs look longer when sitting.
"'The Duchess Slant' is one of the most elegant and flattering ways to sit, because it has a lengthening effect on the legs," she said. "The key with the technique is to square your shoulders straight ahead while maintaining perfect posture. Keeping knees and ankles together at all times, position your legs so that you create a slant, angling your knees to the side. Hands should be folded one over the other and placed in your lap."
And while her slant wasn't perfect, Meghan and Harry were there to support the Queen for a great cause: The Queen, 92, hosted an evening reception for change-makers across the Commonwealth of 53 nations loosely linked to the U.K.
Harry, 33, was named the organization's Youth Ambassador just weeks before he and Meghan, 36, were married on May 19.
For the event she wore a soft pink Prada dress featuring a buttoned bodice and belt as well as black Aquazzura pumps.
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-with reporting from Simon Perry and Maria Mercedes Lara