Hanging out with Richard Nixon’s daughter Tricia at a White House supper-dance, swapping stories with Ronald Reagan about horseback riding and bending the ears of Donald Trump and Joe Biden about climate change, feature among the new King’s encounters with US presidents.

Charles, who became head of state following the death of his mother last week, has made the acquaintance of 10 of the 14 US presidents who have held office since he was born in 1948.

He was just 10 when he checked off his first president in 1959. That was when Dwight Eisenhower visited the Queen and her family at Balmoral Castle in Scotland, where she died on September 8 after a 70-year-reign.

“I guess you can’t start too early,” said Barbara A Perry, director of presidential studies at the University of Virginia’s Miller Centre.

She noted that Charles’ grandson, George, was a toddler when Kensington Palace released a photograph of him shaking hands with Barack Obama during the president’s trip to London in 2016.

Charles never met Harry Truman, Gerald Ford, Lyndon Johnson and John F Kennedy, Ms Perry said.

His encounters with US presidents included what he recalled as an “amusing” weekend visit to the Nixon White House in 1970 with his sister Anne, when the 20-year-old future king – one of the world’s most eligible bachelors – sensed there was an effort afoot to set him up.

“That was the time when they were trying to marry me off to Tricia Nixon,” he later recalled.

The King has chatted to presidents on his visits to the US and met others when they travelled in the UK. He was in the company of Donald Trump, Mr Obama, Bill Clinton and George W Bush when he represented the British monarchy at the state funeral for former president George HW Bush in 2018 in Washington.

Charles met President Joe Biden last year at a climate change conference in Glasgow.

The royal has visited America about 20 times since that memorable first trip in the Nixon years, he told CNN last year.

The royal siblings had been invited to Washington by Mr Nixon’s daughters and son-in-law, Tricia Nixon, Julie Nixon Eisenhower and her husband, David Eisenhower, grandson of president Eisenhower, for that three-day visit in July 1970.

The young VIPs had a packed schedule that included time at the Camp David presidential retreat, a night-time tour of Washington’s monuments, museum visits, a luncheon cruise down the Potomac River to George Washington’s estate at Mount Vernon, Virginia, a dance on the South Lawn for 700 guests, and a Washington Senators baseball game.

Charles and Mr Nixon also met in the Oval Office. But if the president had his heart set a union between his family and the royals, it was not meant to be.

In June 1971, less than a year after Charles’ visit, Tricia married long-time beau Edward Cox in the White House Rose Garden. A decade later, in July 1981, Charles married Lady Diana Spencer. They divorced in 1996.

Mr Nixon, himself, had pushed for Charles to visit the US for the perceived public relations bonanza, according to a January 1970 memo he sent his national security adviser, Henry Kissinger.

“I think this could do an enormous amount of good for US-British relations,” Mr Nixon said.

He wrote that he had been told that Charles “is the real gem” of the royal family and “makes an enormously favourable impression wherever he goes”.

Charles returned the praise in a thank-you note.

“The kindness shown to us at the White House was almost overwhelming and for that we are immensely grateful,” he wrote to Mr Nixon. “Both my sister and I take back to Britain the most heartwarming evidence of what is known as the special relationship between our two countries and of the great hospitality shown to us by you and your family.”

Many of the former Prince of Wales’ conversations with recent US presidents centred on his interest in tackling climate change. Charles has campaigned for the environment for 50 years, but he acknowledged after becoming King that his new role requires that he set aside his activism on that and other issues.

Charles, 73, and Mr Biden, 79, discussed global co-operation on the climate crisis last year while both attended a summit in Glasgow. They also met at Buckingham Palace in June 2021 at a reception the Queen hosted before a world leaders’ summit in Cornwall.

Mr Biden rejoined the 2015 Paris climate agreement after Mr Trump as president withdrew the US from the accord.

Mr Biden and the King spoke on Wednesday, with Mr Biden offering his condolences over the Queen.

Mr Trump has said that during his visit with Charles, the former prince “did most of the talking” and pressed him on climate during a scheduled 15-minute meeting that stretched to 90 minutes in 2019 at Charles’ residence in London.

During a three-day visit to Washington in 2011, Charles, an advocate of environmentally friendly farming, met Mr Obama. In a speech, he praised Michelle Obama’s campaign against childhood obesity and hunger, and US manufacturers’ efforts to produce healthier foods.

He criticised US government subsidies for large-scale agriculture and encouraged increased business and government support for organic and environmentally friendly food production.

In his toast at a White House dinner in 2005, the future king told then president George W Bush that the world looks to the United States “for a lead on the most crucial issues that face our planet and, indeed, the lives of our grandchildren”.

“Truly, the burdens of the world rest on your shoulders,” he said.

In the remarks, Charles also said the trip reminded him of his first visit to America, “when the media were busy trying to marry me off to Tricia Nixon”.

Visiting Mr Reagan in the Oval Office in 1981, the two discussed their interest in horseback riding as a steward brought tea. But it was not served the British way.

Of the experience, Mr Reagan later wrote in his diary: “The ushers brought him tea – horror of horrors they served it our way with a tea bag in the cup. It finally dawned on me that he was just holding the cup and finally put it down on the table. I didn’t know what to do.”