FILE PHOTO: U.S. President Donald Trump meets Britain's Prince Charles as he arrives at Buckingham Palace, in London, Britain, June 3, 2019. / REUTERS/Toby Melville/Pool

Donald Trump may adore Britain's royal family but the brash US leader could not be more different from King Charles III, a passionate environmentalist who is always strait-laced in public.

The monarch is 76 years old, the president 79. They are both wealthy, previously divorced and love Scotland, where Trump's mother was born and Charles spends many holidays.

But there the similarities appear to end, making for strange bedfellows when the king hosts Trump in Britain this week for an unprecedented second state visit.

Trump, a Republican, has described himself as "a big fan" of the politically neutral royal family, including Charles's son and heir to the throne Prince William, and his wife Catherine.

"I've got to know a lot of the family members. They are really great people," Trump said during a visit to his two golf resorts in Scotland in July.

He has acknowledged that he and Charles "have different views" but that they still "get along".

"I think he's a really wonderful guy, we get along, he was a little bit more into environmental restriction than I am," Trump told the right-wing TV channel GB News last year.

The environment, for which the king has long been a keen advocate, is not the only issue where they have diverged.

'Values' 

Charles received Volodymyr Zelensky at his Sandringham country retreat in early March, just days after the Ukrainian president's humiliating dressing-down by Trump at the White House.

It was seen as a symbolic show of support for Zelensky.

The king also subtly defended the sovereignty of Canada, of which he is head of state, after Trump raised the prospect of making the United States's neighbour the 51st state.

"Democracy, pluralism, the rule of law, self-determination and freedom are values which Canadians hold dear, and ones which the government is determined to protect," Charles said during a speech opening the Canadian parliament in May.

He made the 24-hour trip despite still receiving treatment for cancer.

The king is the head of the Church of England, the mother church of global Anglicanism, but sees it as his "duty" to protect religious diversity across the United Kingdom.

Representatives from all of the main religions were invited to his coronation in May 2023, and earlier this year he inaugurated the King Charles III wing of the Oxford Centre for Islamic Studies, an affiliate of the city's prestigious university.

Trump was confirmed into the Presbyterian church, like his mother, who was from the remote Isle of Lewis off Scotland's northwest coast, but in 2020 said he now considered himself a non-denominational Christian.

He professes "to protect the Judeo-Christian values of our founding (fathers)," as he recently stated at the Museum of the Bible in Washington.

During his first term he instituted a so-called "Muslim ban", placing travel restrictions on citizens of several mostly Muslim majority countries.

'Very different'

Meanwhile, Trump has claimed that Christians were "persecuted" under Joe Biden's presidency and he has created a taskforce to eradicate "anti-Christian bias" in a country where two-thirds of the population identifies as Christian.

During his inauguration in January, six months after surviving an assassination attempt, he declared he had been "saved by God to make America great again".

Some among his loyal fan base do think he has a divine right to rule.

Trump, criminally convicted before he returned to the White House over payments to a pornographic actress, does not hesitate to utter insults or obscenities in public.

This is in stark contrast to Charles, who appears consistently courteous in public, even if he is reported to be impatient in private.

Gardening is a topic of conversation they might want to steer clear of.

Charles is a keen gardener who enjoys planting trees at home and during trips abroad.

Trump recently had the century-old White House Rose Garden turned into a patio with chairs and parasols, while a giant 19th-century magnolia was cut down in the spring because it was deemed dangerous.

"King Charles and President Donald Trump are very different personalities," historian and royal commentator Ed Owens told AFP.

"Nevertheless, it is not the king who chooses which foreign dignitaries get state visits and which do not. It is the role of the current government."