The Queen, 92, stood at the dais as she awaited the Trumps, who each shook her hand.
Even amid his bomb-throwing comments about British politics in a tabloid newspaper interview, there was one subject President Donald Trump treated with exemplary graciousness: the queen.
The US national anthem is due to be played as the Queen and Trump inspect the Guard of Honour, before watching the military march past. Elizabeth has met every USA president since Dwight Eisenhower with the exception of Lyndon Johnson, who never visited Britain while in office.
The Trumps had landed in the castle grounds on his official helicopter Marine One, before being taken to the courtyard in a chauffeured Range Rover, where the Queen and the Coldstream Guards were waiting.
The royal communications office said it would not be releasing details of the 48-minute sit-down.
The queen greeted the pair with a smile, although she had earlier glanced at her watch as she waited for their arrival.
"She nearly had to dance around him", Ms James said.
The queen is known to dislike revealing clothing, so it is expected that Mrs. Trump will wear a fashionable but conservative outfit.
For her Scottish arrival, Trump wore pointed-toe camel Manolo Blahnik pumps with matching Michael Kors trousers and a green Burberry jacket, all earth-tone items that blended into the tarmac and only helped her show off the expensive handbag, not hide it. "She felt Trump was true to poor form as he stumbled impolitely through their meeting", our source added. Trump wrote. "I couldn't help but notice how she moved people".
As part of his ongoing working visit to the UK, Trump and his wife, first lady Melania Trump, will join the monarch for tea.
The band played Hands Across The Sea to mark the links between the two countries before she led her guests into the castle for that most English possible of engagements: Tea.
And while the greeting looked friendly, some viewers were left outraged the President and his wife had not curtsied or bowed to the Queen.
Of those, President Obama, George W Bush and Ronald Reagan have all been hosted at Windsor Castle with their spouses.
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