By James Landale

Copyright bbc

“The problem in using the personality of the monarch and the institution of the monarchy is there is a risk that you cross a line and you ask someone who has to remain studiously non-political to transact a political act on behalf of the government.”

Official state visits by US presidents are rare. There have only ever been three: President Bush in 2003; President Obama in 2011 and Trump in 2019. All other visits were official or informal. So this week’s does matter.

But even if it passes off smoothly and gaffe-free questions may remain about its efficacy. “This is very early in Trump’s presidency,” one diplomat said.

“Have we played this card too soon? What do we do for an encore?”