This is why they don't want him in England, and why they've kept sending Katie and Camilla out of the country this year - so it won't look too obvious when they're not available to mee... be anywhere near him.When you elect the guy who admitted to abusing his power to perv on naked women who thought they were in a protected area and complimenting 14-year-old girls on their singing by telling him he would date them in a couple of years (limiting myself to two examples), this is what you get.
As for the Queen herself, she's in her 90's, she also has bodyguards, and, if worse comes to worse, I'd bet that Prince Philip has one punch left in him. He may yet get to cross 'hitting a foreign leader' off his bucket list.
Besides, the Queen has been shaking hands since she was a princess. She may show Trump a thing or two about sneaky tricks.