Trump seems to break royal etiquette for the second time when greeting King Charles

President Donald Trump seems to have broken royal etiquette for the second time on Wednesday (September 17) as he greeted King Charles for the first day of the UK state visit.

On Tuesday evening (September 16), Trump and Melania touched down at London's Stansted Airport for their two-day state visit.

They stayed at Winfield House in Regent's Park before traveling to Windsor Castle for a jam-packed day of events followed by a state banquet on Wednesday evening (September 17).

As Trump and the First Lady arrived at Windsor Castle, they were greeted by the Prince and Princess of Wales as they stepped off Marine One.

They then walked across the grounds of Windsor Castle where King Charles and the Queen were ready to welcome them to the royal residence.

However, it was one moment that occurred as Trump met Charles that people were surprised about.

Trump and Melania are enjoying a state visit to the UK (Chris Jackson/Getty Images)

Shaking Charles' hand with his right hand, Trump can be seen placing his left hand on Charles' arm - something which is discouraged.

According to ITV, Buckingham Palace explain that touching the King is not necessarily a breach of protocol, but the general rule is to limit this to just a handshake.

Essentially, this means no hugs, or arms on the back or shoulders.

Trump isn't the only person to have slightly deviated from etiquette when it comes to meeting members of the royal family.

Ed Sheeran also made a similar error when meeting King Charles in 2017, by shaking his hand and placing his other hand on Charles' arm.

Charles didn't seem too fussed, with Sheeran noting: "He was asking me if I was still selling lots of records and I told him I've got a concert in New York tomorrow, and he was quite surprised I was flying after this."

Trump seemed to break etiquette (Ian Vogler - WPA Pool/Getty Images)

Trump was accused of breaking etiquette earlier in the day, when he was spotted walking ahead of King Charles at Windsor Castle.

It is royal etiquette for people to walk behind King Charles. In the Royal Family specifically, they walk behind the King according to their rank and the order of succession.

Trump has a jam-packed schedule (Kirsty Wigglesworth - WPA Pool/Getty Images)

Trump and Melania are in the UK until Thursday evening (September 18).

Other elements of the royal-focused first day include a visit to the tomb of Queen Elizabeth II in St George’s Chapel, lunch with the royal family, a special Beating Retreat ceremony with a flypast of UK and US F-35 fighter jets and the Red Arrows, and in the evening, to top off the royal celebrations, a lavish state banquet.