All eyes were on the President and the First Lady as they first stepped out of their auto to greet Her Majesty - and many royal-watchers were quick to notice that there was no curtsy from Melania, while Donald did briefly nod his head as he arrived at Windsor Castle.
Trump was in that moment oblivious of the Queen, who in some ways might reasonably be regarded as one of the World's greatest leaders?
Trump walked ahead of the queen while inspecting troops from the Coldstream Guard and did not bow when he met her - a couple of minor protocol breaches - but the meeting went smoothly.
The pair were seen exchanging chit-chat as the band played on. Elizabeth has met every US president since Dwight Eisenhower with the exception of Lyndon Johnson, who never visited Britain while in office.
Queen Elizabeth II watches the Royal Air Force fly past the balcony of Buckingham Palace, as members of the Royal Family attend events to mark the centenary of the RAF on Tuesday in London.
The royal communications office said it would not be releasing details of the 48-minute sit-down.
He told The Sun newspaper before his arrival that he was looking forward to the visit, complimenting the queen and marveling at the lack of controversy associated with her over the years.
"He did literally eclipse her, but I don't think that was deliberate".
"My wife is a tremendous fan of hers". She welcomed former presidents Ronald Reagan, George Bush and Barack Obamain 1982, 2008 and 2016 respectively. The queen wore a bright blue suit, while the first lady was dressed in a cream-colored pencil skirt and matching jacket.
The meeting comes just one day after Trump arrived in London for his four-day visit.
The president added that his wife similarly admires the Queen.
The British Guard of Honor, wearing formal military attire of red coats with fluffy bearskin hats, saluted the Trumps and played the "Star-Spangled Banner" as the Trumps flanked the Queen. Other protestors waited outside Windsor Castle for the president to arrive.
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