As the world stares in disbelief at US President Donald Trump's behaviour over Venezuela and Greenland, King Charles's advisors must be reaching for their paracetamol. In July, he and Queen Camilla are due to jet to Trump's side for a glittering White House ball to celebrate the United States' 250th anniversary of independence. But by the time King Charles has donned his formal Windsor dark blue tailcoat and medals, President Trump may have quit NATO to force the annexation of Greenland ... or even sent in his troops to take it by force. It leaves King Charles in a terrible...