LONDON — What does a British king have in common with the son of a car salesman from Scranton, Pennsylvania? Quite a lot, it turns out.

When U.S. President Joe Biden arrives at Windsor Castle on Monday he will renew an acquaintance with King Charles III which stretches back decades.

Biden has made a point of stopping off in Britain on his way to this week’s NATO summit in Lithuania to fulfill a first bilateral reception with Charles since he ascended the throne, alongside talks with Prime Minister Rishi Sunak in Downing Street. The president missed the king’s coronation in May, where the U.S. was represented by First Lady Jill Biden, and chose not to visit Great Britain during his trip to Ireland and Northern Ireland in April.

Biden and Charles come from wildly different backgrounds but are of a similar generation — the king is six years Biden’s junior — and share a strong commitment to tackling climate change, as well as a deeply-held love of Ireland and Irish culture.

Less welcome may be a shared concern about wayward sons — a topic perhaps best avoided over high tea at the castle.

“They know each other well, they’ll be relaxed with each other,” said Peter Ricketts, a former senior British diplomat who ran the U.K. Foreign Office from 2006-2010. “They know how to play the diplomatic game … not naming any previous U.S. presidents. I think it will be a very friendly, warm, well-thought-out discussion.” 

Biden, a proud Irish-American, has long made clear privately that he is not the biggest fan of the English monarchy. But, he has told allies, he respected Queen Elizabeth II’s leadership and has found common ground with Charles on the need to urgently combat climate change.

Environmental issues will make up the backbone of the two men’s meeting at Windsor on Monday. Biden and Charles will receive a joint briefing from Britain’s Energy Security and Net Zero Secretary Grant Shapps and U.S. Special Presidential Envoy for Climate John Kerry on a trans-Atlantic drive to “accelerate the deployment of literally trillions of dollars” of climate change investment, Kerry told the BBC on Sunday.

Both heads of state have form on environmental issues. King Charles championed the green cause long before it was considered mainstream, and has consistently used his influence to advocate for the environment. Biden has sought to reassert the U.S. role in reducing carbon emissions, rejoining the Paris Agreement on taking office and passing the Inflation Reduction Act — his landmark injection of $500 billion into clean energy and green industries. 

The pair have joined forces on green campaigns before, with TV cameras picking up Biden telling the then-prince at the COP26 climate summit that “we need you badly” in the global drive to lower emissions.

Both leaders have also previously emphasized the importance of engaging business leaders on the subject, as highlighted by the king’s Sustainable Markets Initiative. As head of the Commonwealth, Charles is particularly interested in climate-vulnerable states.

Sense of calm

Beyond environmental matters, the Windsor summit is designed to radiate a restored sense of calm and cooperation between two old allies after a turbulent few years in both British and American politics, and before the potential upheaval of general elections in both countries next year.

“[Charles] has got a pretty rich backstory when it comes to the United States,” added a former royal aide, speaking anonymously so they could be candid about their former employer. “He’s met every president since Nixon. He’s got very, very clear memories of staying at the White House with his sister [Princess Anne] when Nixon was president, and his experience will absolutely inform the sorts of conversations he wants to have.”

Another well-established link between the two heads of state is their dedication to their respective countries’ relationship with Ireland and Northern Ireland, which is also likely to be on the agenda. 

A former Irish diplomat said the king “has very clearly maintained the legacy of his mother, in terms of her very positive influence on improving relations,” and agreed that Charles and Biden “have in common their shared and very constructive interest in Ireland.”

They added this had been underlined by Charles’ engagement with Irish leaders around the time of Queen Elizabeth II’s death and again at the coronation, and in Biden’s case with his visits to Belfast and Dublin to mark the 25th anniversary of the Good Friday Agreement. A visit to Ireland is widely expected to feature in Charles’ calendar next year.

While the tone of interactions between the U.K. government and its nearest neighbors had “warmed” with the signing of the Windsor Framework deal in February, the same ex-diplomat said, both men are likely to be troubled by the ongoing absence of a governing executive in Belfast. 

Photo op diplomacy

At least as important as what the two men actually say will be the optics of the visit.

Simon Fraser, like Ricketts a former head of the U.K. Foreign, Commonwealth and Development Office, noted: “I think what you’re really looking for is the atmospherics, the ceremony, and the expression at the highest possible level of the relationship.”

This has an added significance in the context of this week’s NATO summit, according to Ricketts.

“Britain is the U.S.’ closest ally in NATO, so it’s a very natural occasion for them to talk a bit about that in carefully non-political, non-partisan terms,” he said.

Fraser agreed, predicting the pair will discuss Ukraine, while one serving U.K. diplomat pointed out: “They’re both commanders-in-chief as well as heads of state, and the king takes a very, very close interest in all things defense-related.”

Their closely-related strategic interests are underpinned by a sense of shared perspective as two leaders who have been prominent on the world stage for 40 years or more. Charles, at 74, is more than 30 years older than Sunak, who became Britain’s youngest prime minister in more than two centuries when he assumed office last year.

“They’ve seen an awful lot of change,” said the former Irish diplomat quoted above. “There’s an awful lot of experience and wisdom to draw upon. They’ve both seen a lot in their political lifetimes —particularly when you compare them to the people in government in London.”

Jonathan Lemire was reporting from Washington, D.C. Annabelle Dickson and Charlie Cooper also provided reporting from London.