The brunette beauty wowed in a white Jenny Packham gown that featured stunning floral embellishments at the shoulders and long split sleeves.
The mom-of-three's accessories are what really set the look over the top, as she wore a pair of Princess Diana's earrings, one of Queen Elizabeth II's bracelets and Queen Mary's Lover's Knot tiara. The outing marks the first time Kate has donned a tiara in nearly three years.
In addition to the jewels, the 40-year-old donned the pale yellow Royal Family order and the violet Dame Grand Cross of the Royal Victorian Order sash.
As OK! previously reported, Camilla, 75, always harbored a bit of resentment towards Kate, with one insider claiming she's fearful the Princess of Wales will be front and center at Charles' coronation next year.
"William and Kate's popularity is at an all-time high. The public is far more interested in seeing William and Kate and the children," the source noted to Radar. "[Camilla] feels slighted that more attention is paid to Kate. She fears Kate will steal her thunder."
Even prior to Charles taking the throne, Camilla was allegedly not-so welcoming to Kate.
"The truth is, the very sight of Kate made Camilla burn with jealousy from the beginning. She called her Kate Simpleton behind her back," an anonymous source once claimed. "There was no doubt that Kate was about to become the new People's Princess — the new Diana — and Camilla would cast herself as the evil stepmother."
A separate Radar insider also alleged Kate was set to receive the bulk of Queen Elizabeth's jewels after her September passing since she was "clearly the family favorite."
For more on the royal family, tune into the criticality acclaimed new podcast, "The Firm: Blood, Lies and Royal Succession." Listen below.