The royal family plays a key part in the UK-US special relationship, and Donald Trump is well known for his love of the monarchy.

He boasted he had “automatic chemistry” with late Queen, and has hailed the King as a “really wonderful guy”.

With the controversial Republican politician making the most dramatic comeback in American political history after winning a second term, Charles and Mr Trump will be expected to encounter one another yet again.

President-elect Mr Trump was already feted with a grand state visit to the UK, hosted by the Queen in 2019, making it unlikely he will be invited to make a second one.

Precedent for second-term US presidents who have already made a state visit appears to be tea or lunch with the monarch at Windsor Castle, as was the case for George W Bush and Barack Obama.

But nothing should be ruled out when it comes to Mr Trump.

Foreign monarchs, presidents or prime ministers are invited to visit the King on the advice of the Foreign and Commonwealth Office, so any decision ultimately lies with the Government.

The last outward state visit to the US by a British monarch was 17 years ago when Elizabeth II was hosted by George W Bush in 2007.

The King and Queen could be invited to America by Mr Trump.

Palace officials indicated that after Charles and Camilla’s recent Australia tour that the King will return to regular overseas trips next year as he adapts to living with cancer.

According to protocol, a British monarch waits until the inauguration of a president to send a private message of congratulations, rather than issuing one following the election result.

Mr Trump’s victory marks an extraordinary comeback in a political career which has been marred in controversy, criminal charges, accusations of racism and sexism, and the US Capitol riots in January 2021.

But British sovereigns are well skilled in diplomacy.

The late Queen entertained all manner of controversial leaders over the decades, from Romania’s Nicolae Ceausescu to Russia’s Vladimir Putin.

Mr Trump has often spoken of his bond with Elizabeth II.

“I really got to know her because I sat with her many times and we had automatic chemistry, you will understand that feeling,” he said.

But author Craig Brown, in his new biography A Voyage Around The Queen, has since claimed that the monarch found Mr Trump “very rude”.

She is said to have “particularly disliked” the way he “couldn’t stop looking over her shoulder, as though in search of others more interesting”.

In 2018, Mr Trump joined the Queen for tea at Windsor Castle.

As they inspected a Guard of Honour, the president walked along before standing still in front of the Queen, meaning she had to navigate her way around him so they could walk side by side.

He later said of the sovereign in an interview: “That is a beautiful woman.”

At the state visit a year later, he was treated to a full programme of pomp and pageantry, with a ceremonial welcome and a glittering ballroom banquet at Buckingham Palace.

Charles inspected a Guard of Honour with Mr Trump on the lawns of the royal residence, dined with him at the banquet and had tea with him, Mrs Trump and the then-Duchess of Cornwall at Clarence House.

Mr Trump, who is known for his extreme hand-holding, appeared to deliver a fist bump to Elizabeth II in the Palace gardens, but it was more likely an unusual clench of her hand.

He tweeted the London trip had been a success, adding: “The Queen and the entire Royal family have been fantastic.”

Mr Trump and the King, as the Prince of Wales, have met several times, although not since Charles acceded to the throne in 2022, with Mr Trump’s first term as American leader ending in 2021.

But they appear to be on friendly terms.

Incoming-First Lady Melania Trump wrote in her recent memoir that she and her husband have an ongoing correspondence with the monarch.

“Our friendship with the royal family continues and we exchange letters with King Charles to this day,” she said.

Mr Trump has admitted, however, that the King is “a little bit more into environmental restriction than I am”.

In fact, while Charles has warned climate change is “the wolf at the door”, Mr Trump brands it a “Chinese hoax” and “bullshit”.

But Mr Trump maintained he “totally listened” to the then-prince when he was pressed on climate change by Charles during his 2019 visit.

The King wrote privately to Mr Trump after he survived an assassination attempt, condemning the violence and wishing him a quick recovery.

And Mr Trump spoke of how he hoped the King was “going to be OK” following his cancer diagnosis this year.

He has, however, been publicly critical of the Duke and Duchess of Sussex, who live in the US with their children.

Mr Trump warned Harry he could face consequences if he lied about taking drugs on his US visa application.

This came after Harry’s references to taking cocaine, marijuana and psychedelic mushrooms in his memoir Spare, which prompted a conservative Washington DC think tank to question why he was allowed into America in 2020.

Mr Trump told Nigel Farage on GB News in March: “We’ll have to see if they know something about the drugs, and if he lied they’ll have to take appropriate action.’

Mr Farage asked: “Appropriate action? Which might mean … not staying in America?”

Mr Trump replied: “Oh I don’t know. You’ll have to tell me. You just have to tell me. You would have thought they would have known this a long time ago.”

The Heritage Foundation brought a lawsuit against the Department for Homeland Security (DHS) over access to Harry’s immigration records after a Freedom of Information Act request was rejected.

But in September a US judge ruled Harry’s visa application should remain private despite him admitting taking drugs in his autobiography.

Mr Trump also lambasted Harry and Meghan, accusing them of treating the late Queen “very disrespectfully”.

“She was unbelievable. And I thought she was treated very disrespectfully by them,” he said.

“She, I would say, although she wouldn’t show it because she was strong and smart, but I would imagine they broke her heart.”

According to Meghan’s father, Thomas Markle, Harry once urged Mr Markle to give Mr Trump a chance.

Mr Markle shared details of their private conversation in an interview with ITV’s Good Morning Britain.

He said: “Our conversation was, I was complaining about not liking Donald Trump, he said: ‘Give Donald Trump a chance’.

“I sort of disagreed with that.”

Meghan was a vocal critic of former reality star Mr Trump, backing his rival, Hillary Clinton in 2016, and suggesting then that she would leave the US if he won.

She previously labelled him “divisive” and a “misogynist”.

Mr Trump meanwhile once said he would have slept with Diana, Princess of Wales, without hesitation.

In a Howard Stern radio interview recorded just months after the princess died, he also branded her “beautiful” but “crazy”.

Mr Trump used to bombard Diana – the mother of Harry and the now-Prince of Wales William – at Kensington Palace with massive bouquets, according to broadcaster Selina Scott, who said he saw the princess as “the ultimate trophy wife”.

She added that Mr Trump gave Diana the creeps: “It had begun to feel as if Trump was stalking her.”

Mr Trump also made remarks about the now-Princess of Wales after Kate was photographed sunbathing topless by the paparazzi in France.

“Kate Middleton is great – but she shouldn’t be sunbathing in the nude – only herself to blame,” he wrote on social media.