Meghan Marklehas quickly adapted to royal tradition. She hasperfected the royal curtsy, she’sadopted sheer stockings into her wardrobeand she basicallyhas her PhD in the “duchess slant.”(Well, make thathad.) The newly crowned Duchess of Sussex had a minor slip-up with royal posture protocolduring Tuesday’s party at the Buckingham Palace— andPEOPLE’s Simon Perrycaptured the exact moment she realized it.

After expertlydemonstrating the “duchess slant” at numerous royal eventsin 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 besidePrince HarryandQueen Elizabethat 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, whichsister-in-law Kate Middleton also follows, royal women keep legs and knees together, although crossing at the ankle is fine, which Meganexpertly demonstrated at her solo outing with the Queen earlier this month.

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The Duchess Of Sussex Undertakes Her First Official Engagement With Queen Elizabeth II

Myka Meier, royal etiquette expertand founder and director of Beaumont Etiquette,told PEOPLE earlier this yearthat “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 sharedwith PEOPLE.

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Meier also explained that the slant helpsmake 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 theCommonwealth of 53 nations loosely linked to the U.K.

Harry, 33, was named the organization’sYouth Ambassadorjust weeks before he and Meghan, 36,were marriedon May 19.

For the event she wore a softpink Prada dress featuring a buttoned bodiceand belt as well as black Aquazzura pumps.

–with reporting from Simon Perry and Maria Mercedes Lara

source: people.com