King's speech was a 'high stakes' moment of US visit, Palace says

King Charles III's speech to the US Congress last week was a "high stakes" moment, a senior royal aide has said, but one that stayed true to the monarch's personal "conscience".

The state visit speech, in which the King urged US lawmakers to defend Ukraine and support Nato, was a "measure of how much he personally cares", said the Palace aide.

The speech has been widely applauded for its diplomatic skill in encouraging US President Donald Trump to defend democratic values against aggressors in a "volatile world".

Buckingham Palace has been reflecting on a trip that was the biggest diplomatic challenge of the King's reign.

The King had travelled against a background of political tension between the UK and the US, most recently over the government's decision to not get involved in the Iran war.

Addressing US Congress on Tuesday, the King used humour and charm, but delivered a surprisingly direct message about the need for the US to support democratic values.

"Everything that is in that speech is an observable fact. And so, I think we felt very comfortable with the King speaking as he did," said the royal aide, who said the monarch was guided by a sense of "truth" and "conscience".

The speech had been welcomed by US lawmakers in the Capitol building, with the King receiving 12 standing ovations.

On the personal chemistry between the King and US president, it was more positive than might have been expected, given the differences in the UK and US positions, suggested the royal aide.

"They get on very well... It's a pairing, sort of unlikely though it might be in many ways… I mean, given some of the issues that have presented themselves in the bilateral relationship, you'd think it might all be a bit tricky.

"But far from it. And the warmth that you see in public is absolutely the warmth you see in private. That meeting in the Oval Office, there was an awful lot of warmth and laughter," said the royal aide.

Ahead of the visit, a diplomatic challenge for the UK had been that Trump had been an enthusiastic fan of the King and the monarchy, but had criticised the UK's prime minister and its armed forces.

The state visit had sought to build back bridges between the UK and US, beyond the focus on the royals.

"It's not a competition between the King and the government," said the royal aide.

"The King is there to support the government, to help the government. It was at the government's request, of course, that he undertook this visit."

There were no press conferences during the state visit, but there were still diplomatic eyebrows raised over Trump having seemed to suggest that the King was closer to his own views on the war with Iran.

In his state dinner speech, Trump had said: "We have militarily defeated that particular opponent, and we're never going to let that opponent ever - Charles agrees with me even more than I do - we're never going to let that opponent have a nuclear weapon."