There have been 11 US presidents in office while the Queen has been on the throne, and she has met all of them apart from one - President Trump.

Richard Fitzwilliams royal correspondent says when it comes to meeting the Queen, it is a tradition like no other.

"There is the matter of tweeting, when you are with the queen, it is protocol you don't discuss afterwards to anyone what was walked about, it's a strictly private situation.

LISTEN ABOVE AS RICHARD FITZWILLIAMS SPEAKS TO TIM DOWER