At the end of the recent visit by King Charles III to the White House, President Trump told reporters that the USA needed more people like Charles as US citizens. Trump loves Charles's accent and his intelligent refinement. Charles was Oxbridge educated (Trinity College, Cambridge 1967-70 - see below) . He is not super-intelligent. Not at all. But he is industrious, very thoughtful and sensible. And sensitive to others. He has integrity (which occasionally lags as is the case for all humans).
Charles likes to gently take the piss out of Trump. He does it in a way which is entirely acceptable to Trump because it is refined. You can't criticise Trump or insult him. But Charles ribs Trump is a sophisticated way making it acceptable.
