The younger brother of Princess Catherine couldn't help but gush over the Prince and Princess of Wales following their appearance at the state banquet welcoming President Trump Wednesday.

After Kate and William shared a photo of themselves ahead of the lavish dinner at Windsor Castle on social media, James went into full proud brother mode.

"Ready for The State Banquet 🇺🇸🇬🇧," the Waleses captioned the Instagram post of them at Frogmore House.

"Proud to be 🇬🇧," James, 38, proudly wrote in the comments section.

The banquet was attended by more than 150 people, including royals, politicians, and prominent public figures with ties to both the UK and the US.

For the occasion, the princess dazzled in a couture gown created by British designer Phillipa Lepley, which featured a full-length, hand-embroidered gold Chantilly lace evening coat atop a silk crepe.

The future queen, who has long championed British fashion and craftsmanship, accessorized with diamond earrings that belonged to the late Queen Elizabeth II.

Kate completed her regal look by wearing the Royal Family Order of King Charles III, the Royal Family Order of Elizabeth II, the Grand Cross of the Royal Victorian Order and the GCVO Star and Sash.

Prince William, for his part, wore the traditional White Tie with a Windsor tailcoat, as well as the Most Noble Order of the Garter Sash with the Lesser George Miniature Medals.

During the dinner, which featured heartfelt speeches from Trump and Charles, the princess was seated next to the commander in chief.

Her placement at the dining table underscored just how important her role within the Firm is, as she and Trump were seen exchanging laughs, smiles and even clinking their glasses together during a toast.

At one point in the evening, Trump appeared to make a thinly veiled dig at Prince Harry in his formal address before esteemed dignitaries.

While praising the Prince of Wales, the president said to King Charles that he had raised a "remarkable son" -- with no mention of the king's estranged youngest son, who had quit royal life in 2020 and moved to the US.

Trump also highlighted the king's philanthropic work in a comment that could be seen as a subtle swipe at the Duke of Sussex.

The king "uplifted the poor, cared for rural farmers, and tended to wounded veterans like nobody else," Trump said, before continuing his warm words for the British royals.

He added that the future king, 43, is "going to have an unbelievable success in the future."

"Melania and I are delighted to visit again with Prince William and to see Her Royal Highness Princess Catherine so radiant and so healthy, so beautiful. It's really a great honor," he added.

Trump called the evening "one of the highest honors of my life," telling Charles that he's had "such respect for you and such respect for your country for many decades."

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