Charles described the ties between Britain and the United States as a story of “extraordinary evolution, from overcoming conflict to forging one of the closest and most productive alliances the world has seen.

“Together, we face the challenges of today, and the opportunities of tomorrow,’’ he wrote, adding that he had no doubt the two countries would continue to defend their shared values over the next 250 years.

As an example, Charles pointed to the responsibility to protect nature, an issue that has long been central to the king’s public work.

In April, Charles and Queen Camilla made a multi-day state visit to the United States, where they were received by the president at the White House.

The trip came at a time when relations between the two countries had been strained by issues including the war involving Iran, visiting a delicate diplomatic balancing act for the monarch.

Trump subsequently praised Charles in glowing terms.