London (CNN) Donald Trump limbered up for his latest overseas trip -- to Britain -- in typical style, with remarks that risked insulting his royal hosts and by plunging headlong into the country's fraught domestic politics.

The US President described one of the newest royals, the Duchess of Sussex -- the former Meghan Markle -- as "nasty" when he was told the American had once described him as "misogynistic."

"I didn't know that she was nasty," Trump replied in an interview with "The Sun" newspaper. He then tweeted Sunday morning: "I never called Meghan Markle 'nasty .' "

Even before he landed, Trump and London Mayor Sadiq Khan renewed their long festering spat.

As Air Force One was on its final approach to Britain, Trump hit back.

"@SadiqKhan, who by all accounts has done a terrible job as Mayor of London, has been foolishly "nasty" to the visiting President of the United States, by far the most important ally of the United Kingdom. He is a stone cold loser who should focus on crime in London, not me...." Trump tweeted.

And Trump waded into the Conservative Party's contest to find a new Prime Minister and Britain's paralyzing debate on leaving the European Union, in a way sure to outrage British critics.

Most presidents would go out of their way to avoid such sensitive topics at a moment of extreme political stress. In Trump's case they may deepen his already intense unpopularity in Britain ahead of his arrival for a three-day stay on Monday but enhance his global reputation as an unpredictable, disruptive influence.

Respecting diplomatic niceties has never been Trump's style, and his remarks underscored the intense challenge his visit poses to the "special relationship" between the US and Britain.

Trump's incendiary remarks were conveyed in a pair of bombshell interviews with the "Sun" tabloid and the "Sunday Times" -- papers owned by Rupert Murdoch, the proprietor of Fox News. They came as Britain prepares trademark pomp for Trump, who will be guest of honor at a state banquet hosted by Queen Elizabeth II at Buckingham Palace on Monday, designed to indulge his taste for adulation. First lady Melania Trump will accompany the president to the opulent ballroom.

The President has a habit of ignoring the political and diplomatic sensitivities of his hosts during trips abroad. In Japan just last week, for instance, where he was greeted with supreme flattery and royal ceremony , the President indicated he wasn't much bothered by North Korea's missile tests. His comments did not take into account the fact that such behavior is viewed with alarm and a grave security threat by the government in Tokyo.

Trump's comments ahead of his trip to Britain will also come as a new blow to beleaguered Theresa May, whose premiership has been destroyed by her failure to solve the political crisis provoked by Brexit.

May will trigger a Conservative Party leadership election Friday which will begin a search for her successor and likely produce a new prime minister by the end of the summer. Trump's Washington is clearly rooting for a more openly Euro-skeptic successor to May who could provide an ideological partner more closely aligned with the current White House.

UK has 'got to get it done'

In the Sunday Times interview, Trump suggested that May would have been better off had she adopted his barnstorming negotiating style in intricate exit talks with the EU.

"They've got to get it done," Trump told the paper. "They have got to get the deal closed."

Trump also posed a challenge for candidates battling to become Prime Minister, calling on them to embrace renegade Brexiteer Nigel Farage, whose new party's strong showing in EU elections is posing an existential threat to the Conservative Party.

"I like Nigel a lot. He has a lot to offer," Trump said. "He is a very smart person. They won't bring him in. Think how well they would do if they did. They just haven't figured that out yet."

Farage -- who Trump calls a friend -- is a populist, nationalist leader in the President's own image. Like Trump, he has been accused by critics of using the emotive issue of immigration to advance his own political profile and to create division.

Trump and his national security advisor, John Bolton, have been outspoken proponents of Brexit, given their disdain for international institutions like the EU and attempts to restore national sovereignty rather than multilateral cooperation as the building block of international relations.

The President promised to go all out for a trade deal between the US and the UK if Britain severs ties with the EU.

Trump also warmly praised Boris Johnson , the flamboyant former London mayor who is vying to become Prime Minister, in a remark that looked strongly like an endorsement and struck his critics as meddling in Britain's internal politics.

Johnson "would do a very good job -- he would be excellent," the paper quoted Trump as saying.

Opposition Labour Party leader Jeremy Corbyn, who wants to force a general election to oust the Conservatives, took exception to Trump's comments.

"President Trump's attempt to decide who'll be Britain's next PM is an entirely unacceptable interference in our democracy," Corbyn wrote on Twitter . "The next PM should be chosen not by the US president, nor by 100,000 unrepresentative Tory party members, but by the British people in a general election."

Trump weighs in on Markle

JUST WATCHED Trump calls Meghan Markle 'nasty' on tape, then denies it Replay More Videos ... MUST WATCH Trump calls Meghan Markle 'nasty' on tape, then denies it 04:06

In an interview with "The Sun" published on Saturday, the interviewer mentioned Markle's 2016 comments that his politics were misogynistic and divisive. Trump responded by saying he had not been aware Markle was "nasty."

In another interview with the "Sunday Times," he also seemed keen to smooth over controversy, saying, "I am sure she will go excellently. She will be very good."

Markle is expected to miss the state banquet at Buckingham Palace because she is on maternity leave, but Trump will have tea with her new father-in-law, Prince Charles, during his visit.

There was no immediate reaction from the British government to Trump's remarks. But officials have learned to expect such flagrant interventions in UK politics from the President.

When he was in London last year, the President detonated a huge controversy by criticizing May's Brexit policies in another "Sun" interview. The comments led him into a rare apology to May from Trump, who seemed unusually chagrined over the interview.

There is also a sense that the President is playing to type and the shock value of his remarks is perhaps not what it was during the early years of his administration.

JUST WATCHED Trump attacks London mayor in tweets before landing Replay More Videos ... MUST WATCH Trump attacks London mayor in tweets before landing 01:46

Trump is not the first US President to weigh in on Brexit. President Barack Obama's comment before the 2016 referendum that Brexit Britain would go "to the back of the queue" regarding a trade deal with the US was criticized by opponents in the UK and the US. But it was an isolated incident that pales into comparison with Trump's frequent interventions into UK politics.

Trump's remarks will fuel what are expected to be intense protests in London during his three-day visit to the United Kingdom, which is laying on an intense security net in central London.

But Trump, who loves nothing more than to be the center of attention, could not capture the main headlines in Britain Sunday morning.