Inside King Charles' Congress speech: Three lines that stopped the room

The British monarch, King Charles, has delivered a powerful speech to Congress as part of his visit to the US to celebrate the 250th anniversary of American independence.

It is the second time a British monarch has delivered such a speech to both houses of Congress.

Charles, 77, said that despite uncertainty and conflict in Europe and the Middle East, the UK and the US would always remain staunch allies in defense of democracy.

The monarch dropped powerful lines during his historic address that stopped the room for a while.

The King talked of the need for an international rule of law and the importance of a shared belief in "democratic, legal and social traditions".

While warning against isolationism, the royal said with such shared historical and philosophical roots, "our two countries have always found ways to come together.

There was even room for a gag about the US being a young country, as it marks its 250th anniversary.

"That's 250 years, or as we say in the United Kingdom, just the other day," the King said, getting a big laugh in response.

He told the US Congress 'acts of violence will never succeed' after attack on Trump.

After the strained UK and US relationship of recent months. He used his own prestige and Trump's fascination with monarchy to rebuild a sense of transatlantic trust.

He also touched on the importance of trade between the two countries in reaction to Trump's repeated threats to impose tariffs on countries around the world.

"More broadly, we celebrate the $430bn in annual trade that continues to grow, the $1.7 trillion in mutual investment that fuels that innovation, and the millions of jobs on both sides of the Atlantic supported across both economies," King Charles said in his speech.

He added, "From the depths of the Atlantic to the disastrously melting ice-caps of the Arctic, the commitment and expertise of the United States armed forces and its allies lie at the heart of Nato, pledged to each other's defence, protecting our citizens and interests, keeping North Americans and Europeans safe from our common adversaries."

The King also made mention of his mother, saying: "When my mother visited in 1957, not the least of her tasks was to help put the special back into our relationship after a crisis in the Middle East."

"Nearly 70 years on, it is hard to imagine anything like that happening today," he noted.

"But it is not hard to see how important the relationship remains, in matters both seen and unseen."

Being passionate about the environment, the King also touched on the "natural wonders" of the US and placed heavily emphasis on protecting the environment.

"Yet even as we celebrate the beauty that surrounds us, our generation must decide how to address the collapse of critical natural systems which threatens far more than the harmony and essential diversity of nature," said the King.

He added, "We ignore at our peril the fact that these natural systems, in other words, nature's own economy, provide the foundation for our prosperity and our national security."

King Charles made sure to crack a joke here and there during his speech, and one involved Trump's controversial East Wing ballroom project for the White House. He even made a reference to a time when British troops actually set fire to the White House.

"I cannot help noticing the readjustments to the East Wing, Mr. President," King Charles said to Trump. "I'm sorry to say that we British, of course, made our own small attempt at real estate development of the White House in 1814."

Menawhile, during a state dinner at the White House, Trump said, “Charles agrees with me even more than I do. We’re never going to let that opponent have a nuclear weapon.”