King Charles III and Queen Camilla are concluding their four-day state visit to the US, bidding farewell to President Donald Trump and First Lady Melania Trump.
The trip, which comes as the US approaches the 250th anniversary of its independence from Britain, is aimed at celebrating the strong relationship between the two countries.
"The greatest king in my book," Trump said as they posed for photos outside the White House on Thursday.
The King and Queen went on to visit the Arlington National Cemetery, where the monarch laid a wreath at the Tomb of the Unknown Soldier.
On Wednesday, the Royals attended a ceremony at the National September 11 Memorial in New York City, accompanied by former New York Mayor Michael Bloomberg.
The Royals left a bouquet of flowers with a note at the memorial.
They also met families of victims and first responders who were involved in the rescue efforts after the attacks, as well as currently serving personnel.
The royal couple's day out in New York also saw Queen Camilla visiting the New York Public Library to attend a literary event held by her charity, The Queen's Reading Room, where she met Sarah Jessica Parker and Anna Wintour.
Meanwhile, King Charles visited Harlem Grown, a socially-focused local community organisation in Upper Manhattan.
The King and Queen ended their third day at the Rockefeller Center where they celebrated 50 years of the King's Trust charity at an event attended by global ambassador Lionel Richie.
The previous evening saw a lavish state banquet, an aircraft flyover at the White House, and a speech from the King to Congress.
During his address to the state dinner, Trump described the history and bond between the US and UK "a friendship unlike any other on Earth", as well as praising golfer Rory McIlory, who was in attendance.
Before entering the White House, the president praised the King's speech to Congress, saying he had made him "very jealous".
The King responded with his own speech, making jokes about White House renovations and Winston Churchill.
Earlier, the King had arrived in the House of Representatives chamber to applause from hundreds of onlookers, including top US officials.
He followed in the footsteps of his late mother, Queen Elizabeth II, who had addressed the chamber in 1991.
In his speech, the King said the destinies of the US and UK had been interlinked ever since America's independence.
"As Oscar Wilde said, 'We have really everything in common with America nowadays except, of course, language!'" the King joked to laughter from his audience.
King Charles promoted the importance of protecting the environment.
"As we look toward the next 250 years, we must also reflect on our shared responsibility to safeguard Nature, our most precious and irreplaceable asset," he said.
The statement received a standing ovation.
The King concluded with a message of unity:
"I pray with all my heart that our alliance will continue to defend our shared values, with our partners in Europe and the Commonwealth, and across the world, and that we ignore the clarion calls to become ever more inward-looking."
Earlier in the day, King Charles and President Trump held a closed-door meeting inside the Oval Office of the White House.
Senior British and American officials were also present during the meeting.
On Tuesday morning, the royals received a ceremonial welcome at the White House, where President Trump presented a military spectacle to the King and Queen, including gun salutes and bugles.
President Trump gave a speech in front of the White House, in which he joked it was a beautiful British day - an apparent reference to the rainy conditions, which drew laughter.
Trump said the King's speech to Congress later was "going to make everyone very envious of that beautiful accent".
"He's a very elegant man," Trump said, before describing "the noble spirit of the British" and discussing the UK and US's shared history.
Following Trump's remarks, the King, Queen, president and first lady walked up the steps to the balcony overlooking the White House South Lawn to observe a flyover and troops marching below.
The previous day, the Royals arrived in the US by plane at Joint Base Andrews, Maryland, to a waiting red carpet.
After walking through a guard of honour, a military band played both the US and UK national anthems.
The royal couple then went on to meet Donald and Melania Trump at the White House for afternoon tea.
The King and Queen attended a British embassy garden party, where the King chatted with former speaker of the House of Representatives Nancy Pelosi among other guests.
The royal couple finished their State Visit with a community party and parade in the small town of Front Royal in Virginia, before waving goodbye and boarding a plane that will take them on to their next destination - Bermuda.
