The King's speech to Congress on Tuesday is expected to reaffirm the UK and US's shared democratic values, woven deep into the fabric of both nations over the past 250 years.
He will open the address by referencing the events of Saturday evening, in a spirit of solidarity, sympathy and support, as he brings "the highest regard and friendship of the British people to the people of the United States" in this landmark anniversary year.
The bulk of His Majesty's speech, written on the advice of the Government, will reflect the great challenges, both nationally and internationally, that we currently face.
Charles will reflect that while the UK and US have not always agreed on everything, the foundations of our "democratic, legal and social traditions" - stretching all the way back to the Magna Carta - are such that "time and again, our two countries have always found ways to come together".
He is expected to say that when we come together, the results are not just of national but global benefit.
Other themes that will be touched upon in the 20-minute speech will be the importance of trade and technology, the environment and the King's own faith.
Charles will reflect on his own service in the Royal Navy, despite President Trump's dismissal of the UK's naval capabilities, referring to its aircraft carriers as "toys", adding that "our defence, intelligence and security ties are measured not in years but in decades".
The King is expected to conclude by noting that the story of our two nations over the last 250 years is one of "reconciliation and renewal", giving rise to "one of the greatest alliances in human history" - an alliance which His Majesty hopes and prays will continue to protect and celebrate the values he has referenced, long into the future.
