Biden appeared to break royal etiquette rules as he greeted King Charles during his visit to the UK

• President Biden met King Charles III at Windsor Castle on Monday during his visit to the UK.
• Biden touched Charles' arm and put his hand on Charles' back, which breaks royal etiquette rules.

President Joe Biden appeared to break royal etiquette rules during his visit to the UK on Monday, greeting King Charles III by touching the king's arm and putting his hand on his back.

Biden met with the king and the UK's prime minister, Rishi Sunak, in a trip that the White House said was intended to "further strengthen the close relationship between our nations," Reuters reported on Sunday.

Biden kicked off the trip with a "low-key meeting" with Sunak at Downing Street in London, according to Reuters. He then traveled to Windsor Castle, just outside of London, to have tea with the king and view an exhibition of items relating to the US in the castle's White Drawing Room, according to a Buckingham Palace press release.

During their meeting, Biden was photographed shaking Charles' hand and placing a hand on his back rather than taking part in a traditional bow.

Touching a member of the royal family when they have not initiated contact is considered a breach of royal etiquette, former royal butler Grant Harrold previously told Insider. Harrold, who worked for Charles between 2004 and 2011, said members of the public who meet the royals should always wait for them to initiate a handshake.

Bowing or curtsying isn't strictly necessary when greeting a royal, but the royal family's official website says that "many people wish to observe the traditional forms."

Charles and Biden have met before on several occasions, including at the G7 Leaders Summit in Cornwall, England, in June 2021 and at COP26 in Glasgow, Scotland, in November 2021.

The president and first lady also attended the funeral of Queen Elizabeth II on September 19, 2022. However, as Insider previously reported, Biden didn't attend the king's coronation in May as it is considered against tradition for US presidents to attend. The first lady and her granddaughter Finnegan Biden attended instead.

It's not the first time a US president has broken the unspoken rules of meeting royals

Biden also kept his sunglasses on while meeting Queen Elizabeth II in 2021, and President Donald Trump appeared to break royal protocol several times during his UK visits in 2018 and 2019, walking in front of Queen Elizabeth and appearing to touch her back at a state dinner.

Michelle Obama also caused controversy when she put her arm around Queen Elizabeth at Buckingham Palace in 2009 during her first royal visit as first lady.

Obama wrote in her 2018 memoir, "Becoming," that she and the Queen bonded over both wearing uncomfortable high heels, and she didn't realize until later that she had committed "what would be deemed as an epic faux pas."

"If I hadn't done the proper thing at Buckingham Palace, I had at least done the human thing," she wrote. "I daresay the Queen was okay with it, too, because when I touched her, she only pulled closer, resting a gloved hand lightly on the small of my back."

Buckingham Palace and the White House did not immediately respond to Insider's request for comment.