1. Tricky visit with unprecedented degree of difficulty

The contemporary political historian Anthony Seldon said the 27-30 April visit was “obviously beyond tricky” and had a “degree of difficulty” vastly surpassing any official visit since the first one by a reigning monarch, when George VI met Franklin D Roosevelt to persuade him to enter the second world war. “Because you are dealing with somebody who is so unpredictable,” Seldon said.

He said relations with the US had gone through difficult periods before: Lyndon B Johnson and Harold Wilson, Richard Nixon and Edward Heath, Dwight Eisenhower and Anthony Eden – the latter leading to Eden’s ousting after the Suez crisis. “So it’s a tense moment. But there have been tense moments in the past. And it will be fascinating to see how the monarch plays it.”

Seldon said since Charles was “probably the one person in the world who Trump doesn’t want to offend”, the president would operate “within tramlines”, thus giving the king “more leeway”.

On the “most important visit of the king’s life”, Charles could “either be very cautious and safe, or he can remind the American people of the basis on which the United States was formed 250 years ago”, Seldon added. He said values shared with the UK were of a country that moved away from arbitrary power on the basis of separation of powers, with the bill of rights at its heart; individual rights, limited government, rule of law, enlightenment values. Not to mention a shared history stretching back centuries.

Prof Philip Murphy, the director of history and policy at the University of London, said the risk was more significant for Keir Starmer than for Charles, particularly after the Peter Mandelson and Olly Robbins controversy. “It’s another aspect of this desperate desire to court Trump and to take really significant risks,” he said.

“They’ve risked the prestige of their head of state, they’ve put his dignity in peril by putting him in contact with Trump, who is both hugely controversial and a very tricky person to deal with in public,” Murphy said.

2. King’s security taken ‘very seriously’

Charles’s visit will have “appropriate security in place in relation to the risk”, a minister said on Sunday after Donald and Melania Trump were evacuated from the White House correspondents’ dinner on Saturday evening when the event was interrupted by gunfire.

Darren Jones, the chief secretary to the prime minister, told the BBC’s Sunday with Laura Kuenssberg programme that further discussions about the king’s security would take place on Sunday. Asked if that meant there would be any escalation of what had already been planned, he said: “There’ll be appropriate security in place in relation to the risk.”

Jones told Sunday Morning with Trevor Phillips on Sky News: “As you would imagine, the government and the palace take the security of his majesty very seriously, and there were already extensive discussions taking place, which will continue over the coming days.”

A Buckingham Palace spokesperson confirmed that talks were ongoing, saying: “A number of discussions will be taking place throughout the day to discuss with US colleagues and our respective teams to what degree the events of Saturday evening may or may not impact on the operational planning for the visit.”

3. The king’s most important speech yet

Charles’s address to a joint meeting of Congress will be televised internationally and is possibly his most important to date. According to Buckingham Palace, he will “recognise the challenges that our countries face”. But Trump notoriously easily takes offence.

When Queen Elizabeth II addressed Congress in 1991, she said power that grew “from the barrel of a gun” never grew well “nor for very long”, and spoke of the importance of Nato; of how Europe could become more open, liberal and aligned with the US; and of the importance and value “of the rich ethnic and cultural diversity” of both countries.

“That would be taken as a direct attack on Trump now,” Murphy said. “What Charles will, I’m sure, do is try and appeal almost over the head of Trump to the American public.” He could stress common values: belief in freedom, belief in democracy, a long history of friendship. “It’s almost saying, without saying it, that Trump is here, but Trump will go and there are longer cultural and political affinities there. He can do it in a way that a political leader can’t. He can make it appear that the strength of the relationship is beyond politics.”

Seldon said there was no need for Charles to even mention Trump, so leaving it up to individuals to see whether the “current chief executive of the US is aligning himself with those values”.

“I think [the address] could be so oblique, and done very deftly, gently, and in a polite and respectful way. The right speech, respectfully delivered, could help. And it can certainly help remind American people about the deep, profound bonds – intellectual, humane bonds – that unite both countries.”

4. Will private remain private?

Undoubtedly with Volodymyr Zelenskyy’s outrageous humiliation in mind, Charles’s Oval Office bilateral has been organised to take place in private after a grip-and-grin photo call. The king, the head of state and of the armed forces, enters knowing Trump has publicly insulted his UK prime minister and mocked the UK military. And Charles is also king of Canada, a country subjected to severe provocation by Trump.

However the king broaches these, if indeed he does, he needs to tread carefully with a president who shoots from the hip and loves speaking to cameras and posting on Truth Social. Murphy said: “He’ll [Charles] be very careful about what he says, because it may very well be reported back. I don’t think Trump has a strong sense of what is private and what is not.”

5. The ghost of Epstein and shadow of the Sussexes

After Andrew Mountbatten-Windsor’s arrest on suspicion of misconduct in public office over his connection with Jeffrey Epstein, the US congresswoman Ro Khanna and Sky Roberts, the brother of the late Virginia Giuffre, urged Charles and especially Camilla to meet Epstein survivors.

No such meeting will take place, a palace source has said, on the grounds it could jeopardise police inquiries and potential legal action, “to the detriment of the survivors themselves in their pursuit of justice”.

If there are protests, the king and queen will be shielded from them. The itinerary offers few opportunities for the couple to come face to face with the public. A visit to a “block party” in Virginia is likely to be the only one.

Murphy said: “There will clearly be press comment. There may be some sort of public protests about it. If he walks around in crowds, people might call out.”

But many Americans may only have seen media coverage of Charles recently in the Epstein or Sussexes context. “So, one talks about the risks, but there’s also a benefit for him here. After a really rough time around Andrew, Harry and Meghan, he can show that he can actually play a valuable role, a role that transcends politics,” Murphy said.

And what about the Duke and Duchess of Sussex, in west coast Montecito almost 3,000 miles from Washington DC? It is understood there are no plans for a father and son reunion during the visit. The best the palace can hope for is no ill-timed soul-baring interviews by Harry, especially on the subject of his royal upbringing.