Also in attendance was Harry's new wife, Meghan Markle.
While walking into the prestigious wedding, the Duchess of Sussex suffered a wardrobe malfunction of her own.
Meghan opted for a $700 dark navy Club Monaco dress for the occasion, and the button up accidentally flashed her bra, as she waved to well-wishers singing her Happy Birthday.
Royal-watchers were quick to pounce on the Duchess’ apparent faux pas calling it a ‘wardrobe malfunction’.
Related: Prince Harry's best man speech at friend's wedding shared online