Pippa Middelton being accused of wearing a "false bottom" at royal wedding Credit: Chris Jackson/Getty; Pascal Le Segretain/Getty (inset)

It's been three years since the royal wedding, but royal watchers are still talking about Pippa Middleton's derriere.

Kate Middleton's sister has been accused of enhancing her backside, which became famous when she followed her sister into her wedding to Prince William in April 2011 in a stunning well-fitted white Alexander McQueen dress.

Stephane Bern, A Knight of the Order of Grimaldo in Monaco and an etiquette expert, argues that Pippa, 30, wore a "false bottom" for the big day.

"Of course she had a false bottom,” Bern said on his talk show on channel France 2. "I repeat it: she had a false bottom. You take her away from that and she has normal buttocks."

Bern added: "It was an optical illusion; she knew there were a billion people watching. It was the moment to show it."

The younger sister to the Duchess of Cambridge isn't unfamiliar with such accusations.

Middleton joked about the world's fascination with her backside during her first-ever public speech on Feb. 25, 2014, at an event in London, laughing: "As I have found out, recognition has its upside, its downside andyou may sayits backside."