The King is being deployed to the US between 27 and 30 April to sprinkle some royal magic over a president who is a monarchist and appears to soften in front of pomp and ceremony.
And the King will have some heavy lifting to do to make President Donald Trump look more warmly on the UK and its government.
The problem is that royal overseas tours can be exposing. They exist against the backdrop of whatever problem or crisis is engulfing the royal family or government back at home.
State visits are not an escape from problems, they often highlight them. It means that this visit is happening against a heap of background noise.
Front and centre is the fact that the King and Queen will be visiting a president currently leading a difficult and controversial offensive against Iran.
This is a visit to a president at war and one who is happy to lash out at those he feels aren’t supporting him.
On a personal level, President Trump’s tone will not have pleased the King. On a professional level, as a constitutional monarch, it is not his job to judge but to support the UK government.
And the government wants the King in America to steady a bumpy friendship.
Next up, Andrew Mountbatten-Windsor, who is now a central issue for the royal family.
The King and Queen will spend time in Washington DC at the White House. But just a mile and a half up the road stands the US Congress, where several lawmakers want the King’s younger brother to give evidence about his relationship with Jeffrey Epstein.
This is a deeply uncomfortable part of the visit.
Buckingham Palace has made no official comment since the former Duke of York’s arrest in February. While the legal process continues, that position will not change.
Then enter the Duke and Duchess of Sussex and their two children.
The King will be on a different coast but will be in the same country where his son Prince Harry and daughter-in-law Meghan now live. The King has only met his granddaughter, Lilibet, once.
There was speculation that there could be scope for a family reunion Stateside. But the King is not expected to meet the Duke of Sussex, during his stay, the BBC understands.
The US marks its 250th anniversary of independence this year – and that will be a significant focus of the trip, with Buckingham Palace saying the trip will “celebrate the historic connections and the modern bilateral relationship” between the countries.
It is also expected that King Charles will deliver an address to Congress.
It is important to remember that royal visits have regularly taken place when the political mood is turbulent.