King Charles will start his State Visit to Washington following an extensive programme of 'Trump-proofing' work by aides in Buckingham Palace, Whitehall and across the Diplomatic Service.
The unpredictable US President will host the King and Queen Camilla on Monday for a private tea at the White House, a garden party and a ceremonial military review, before Charles delivers an historic joint address to Congress on Tuesday.
Behind the scenes there has been frantic co-ordination between the Palace, the Cabinet Office and the British Embassy in Washington to devise what one royal source described last night as 'mitigations' against an embarrassing outburst by the increasingly erratic President.
The visit comes after months of mounting tensions between Trump and Sir Keir Starmer over his refusal to join the war on Iran, the UK's attempt to surrender the Chagos Islands and the fiasco of Peter Mandelson's short-lived tenure as UK Ambassador to the US.
The US Government added to the pressure on the visit last week by suggesting that it would withdraw support for Britain's sovereignty over the Falklands in retaliation for the UK's lukewarm backing for the war.
Barely 24 hours before the Falklands threat was revealed, officials had held one of the final planning meetings for the trip in which a royal representative had asked a British diplomat in America about how to avoid 'unpleasant surprises'. After the diplomat had offered honeyed reassurances, the royal representative is understood to have said: 'Don't make promises you can't keep'.
The 'mitigations' have included talks about restricting the amount of public time between the King and Trump, with an emphasis on private interaction away from the cameras. Discussions have also settled on delivering so-called 'easy wins', in which Charles raises issues unlikely to prove controversial in the Oval Office.
This is expected to include sentiments on passing on the world to the next generation in better shape: although given the King's strong views on the environment, and Trump's scepticism about climate change and related matters, even that is not without its risks.
King Charles, pictured with US President Donald Trump at the latter's State Visit to the UK last September, has had his reciprocal trip subject to 'Trump-proofing' by officials
British and American flags flew from a Washington, DC, lamppost this week in preparation for the King's State Visit
A source said: 'The trip was too far advanced by the time the Iran crisis blew up to stop it. So we are having to Trump-proof it as much as that is possible, to make it as much about Charles and Camilla and as little about the President as is viable in the circumstances.'
However, a royal source told the MoS that it was 'not right' to say that the preparations had been framed by a feeling of 'trepidation'.
The source said: 'If state visits were easy, there wouldn't be much point in doing them. The Trump visit here last year was a success, and helped to reset, rebuild and renew relations, and we hope that this outward visit will do the same.
'It is obviously not without complexity, but we have done our best to mitigate the risks and maximise the opportunities, in the hope it will deliver similarly positive results for the UK.'
The visit will also include a bilateral meeting between King Charles and the President, during which Queen Camilla and the First Lady are expected to hold their own separate meeting. After the King becomes only the second British monarch to address a joint session of Congress – Queen Elizabeth II did so in 1991 – the couple will return to the White House for a state dinner.
Before departing from Washington, the royal couple will lay a wreath and flowers to honour fallen service members, before moving to New York City to meet the families of victims of the terrorist attacks on 9/11. While in New York, the King will also visit a community organisation which teaches children and young people affected by food insecurity 'sustainable urban farming'. He is expected to highlight environmental and social causes while there.
Queen Camilla will attend an event celebrating the countries' shared love of literature, including A.A Milne's Winnie‑the‑Pooh stories, which celebrate their 100th anniversary this year.
The tour ends in Virginia, where the King and Queen will watch performances by Appalachian cultural groups and take part in a community party celebrating America's 250th birthday. They will then depart for the British overseas territory of Bermuda.
President Trump told the BBC last week he hoped the visit could repair relations with the UK, and described Charles as 'a fantastic man'. He added: 'I know him well, I've known him for years. He's a brave man, and he's a great man.'