Donald Trump and First Lady Melania Trump welcomed King Charles III and Queen Camilla to the White House on Monday for the opening day of their state visit.

It wasn't long before the US president breached royal protocol.

Following the couple's arrival in the US, they made their way to the White House's South Lawn for a reception, where they were met by the President and photographed together.

Donald Trump offered the King a firm handshake while the First Lady kissed the Queen on both cheeks - the couple then stood for photographs as they exchanged pleasantries.

Once the pictures had been taken, they turned to proceed inside the White House's main residence for a garden party. As Trump pivoted to make his way forward, he tapped the King on the shoulder.

This gesture breached royal protocol, violating the unwritten rule against initiating physical contact.

While the movement could be interpreted as a sign of warmth, body language expert Judi James told the Daily Mail: "This touch on the arm as they walked in also looked like a more political gesture.

"It was also the first real gesture of active, 'special' friendship here from a rather more subdued Trump than the very effusive rituals we saw during their last meeting [in September 2025]."

James noted that the King appeared unfazed by this breach of protocol.

"Charles has always seemed more relaxed about that than his mother [Queen Elizabeth II], and Trump's gesture was extremely tempered for Trump.

"Just a light, tentative and rather polite touch to steer Charles inside," James added.

She noted that the handshake exchanged between the pair lasted approximately eight seconds and seemed businesslike, while Melania contributed a more informal atmosphere to the reception.

"This initial greeting ritual gave the surface impression of geniality, and the cheek kisses from Melania created the impression of warmth, with an almost "family" style approach," James said.

This marks not the first occasion Trump has been observed breaching royal protocol with British monarchs.

During a state visit to the UK in July 2018, he was photographed turning his back on the Queen and striding ahead of her as they walked past the troops.

He also seemed to contravene protocol during his visit to London last year, when he grasped Charles above the elbow.

The King and Queen's state visit follows shortly after a security incident at the White House Correspondents' Dinner, during which a suspect discharged gunshots in an alleged assassination attempt.

Notwithstanding this, the visit has proceeded and the couple face a packed itinerary.

On Tuesday, Charles will address Congress, representing the second occasion a British monarch has done so, the first being his mother in 1991.