The President of the United States and the First Lady landed at Stansted Airport on Monday morning and then traveled via helicopter to the US ambassador's residence in London. Then followed the welcome ceremony at Buckingham Palace with Prince Charles and Duchess Camilla and, of course, Queen Elizabeth II. The moment when the Queen greeted President Trump was caught on camera and the way he greeted her upon his arrival was picked up on by royal experts.

President Trump is greeted by Queen Elizabeth II during his State Visit. (© Getty Images)

President Trump shook Queen Elizabeth's hand: a breach in protocol?

President Trump, as well as his wife, opted to greet the Queen with a handshake instead of the traditional bow and curtsy. As it turns out, this was NOT as much of a faux pas as many thought. According to the royal family's website, there are, in fact, "no obligatory codes of behaviour when meeting the Queen or a member of the royal family, but many people wish to observe the traditional forms. For men this is a neck bow (from the head only) whilst women do a small curtsy. Other people prefer simply to shake hands in the usual way."

Melania Trump, Queen Elizabeth II and Preisdent Trump during the national anthem of the United States. (© Getty Images)

POTUS and Melania Trump went on to have a private lunch with the Queen and Prince Harry and then were taken to Westminster Abbey by Prince Andrew for a quick tour and to lay a wreath at the Grave of the Unknown Warrior

President Trump, Queen Elizabeth II, Melania Trump, Prince Charles and Duchess Camilla before the State Dinner at Buckingham Palace. (© Getty Images)

The Trumps then had afternoon tea at Clarence House with Prince Charles and Duchess Camilla before going back to Buckingham Palace for a big state banquet where POTUS addressed Queen Elizabeth in a speech: "Your majesty, Melania and I are profoundly honoured to be your guests for this historic state visit. Thank you for your warm welcome, for this beautiful weather, your gracious hospitality, and Your Majesty's nearly seven decades of treasured friendship with the United States of America".