The 59-year-old appeared completely unaware of her wardrobe faux pas, and carried on smiling for photographs enthusiastically.
In a recent podcast, Pod Save The Queen, it was recently discussed on how Fergie was feeling when she was invited back into the fold as a guest of Meghan and Harry's wedding.
"She was doing these little baby waves and a slightly creeping walk. She was clearly doing a good act of lowering her own status, it was as though she was creeping in via the servants’ entrance," says body language expert Judi James.
"It’s interesting how much effort she was putting into looking that brave.”