In a extensive interview with with the popular Murdoch-owned British tabloid the Sun, Trump landed a double blow to embattled UK Prime Minister Theresa May, criticizing her handling of Brexit and saying her plans for a "soft Brexit" would kill any hopes of a trade deal with the US, suggested former foreign minister Boris Johnson, who quit May's cabinet on Monday, would be a better leader than May, and criticized London Mayor Sadiq Khan as "terrible" and unwelcoming.

Trump said that while he likes May, she didn’t listen to his advice on Brexit, and that her Brexit deal isn’t what the U.K. voted for, and warned she may have killed any chance of a key US trade deal.

His comments come at the start of a three-day tour of the U.K., which includes dinner at Blenheim Palace, the birthplace of Winston Churchill, and tea with Queen Elizabeth II at Windsor Castle. And, of course, Theresa May herself.

May had been hoping to impress Trump and use the visit to push for a trade deal with the U.S. after the U.K. leaves the European Union next year, in a process known as Brexit, however that may no longer happen as a result of Theresa May's proposed "Soft Brexit" deal with the EU.

Trump told The Sun: "If they do a deal like that, we would be dealing with the European Union instead of dealing with the UK, so it will probably kill the deal."

Speaking of May's negotiations with the EU, Trump said "I would have done it much differently. I actually told Theresa May how to do it but she didn’t agree, she didn’t listen to me. She wanted to go a different route. I would actually say that she probably went the opposite way. And that is fine."

“She should negotiate the best way she knows how. But it is too bad what is going on.”

A big US-UK trade deal, long promised by Mr Trump, is cherished by Leave campaigners as Brexit’s biggest prize. But the President said Mrs May’s plan “will definitely affect trade with the United States, unfortunately in a negative way" explaining that "we have enough difficulty with the European Union."

“We are cracking down right now on the European Union because they have not treated the United States fairly on trading. “No, if they do that I would say that that would probably end a major trade relationship with the United States.”

No deal with the U.S. can be signed until after next March 29, when the U.K. is to formally leave the EU. Free trade agreements typically take years to conclude and any accord is likely to include hard negotiations over tariffs in industries such as automotive and agriculture, including chlorinated chicken and genetically modified crops.

Despite the withering criticism of May’s Brexit strategy, Trump insisted he still thinks she is “a very good person” and denied claims that she bores him. Asked about a report in The Washington Post that he thinks of Mrs May as “a bossy schoolteacher”, Trump said: “No, no, no, no. I never said anything bad about her.

“That is fake news. I think she is a nice person. I get along with her very nicely. The Washington Post is totally fake. They are just a lobbyist for Amazon." Then, recalling a visit to one of his luxury golf resorts in Scotland two years ago, Mr Trump said: “I predicted Brexit."

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According to the Sun, "Trump's interview will pour nitroglycerine on the already raging Tory Brexiteer revolt against the PM." And, as Axios World Editor David Lawler writes, "May is in the fight of her life with hardliners within her own party, and President Trump — while visiting the U.K. — has just openly sided with the rivals that may attempt to force her from power."

And in more remarks that will set off alarm bells in No10, Mr Trump also said Mrs May’s nemesis Boris Johnson - who resigned over the soft Brexit blueprint on ­Monday - would “make a great Prime Minister."

In the interview, Trump said Johnson has “got what it takes and I think he has got the right attitude to be a great prime minister." He also described the former Foreign Secretary as “a very talented guy”, adding: “I like him a lot.”

“I have a lot of respect for Boris. He obviously likes me, and says very good things about me. I was very saddened to see he was leaving government and I hope he goes back in at some point. I think he is a great representative for your country.”

Asked if the ex-minister could be in No 10 one day, he replied: “Well I am not pitting one against the other. I am just saying I think he would be a great Prime Minister. I think he’s got what it takes."

Trump also said that he will be largely staying away from the capital to avoid huge street protests of up to 200,000 today. But he blamed them on politicians, singling out his nemesis, Mayor of London Sadiq Khan.

Revealing he has been told of the 20ft “Trump Baby” blimp that will be flown above Parliament Square today, he said: “I guess when they put out blimps to make me feel unwelcome, no reason for me to go to London.

“I used to love London as a city. I haven’t been there in a long time. But when they make you feel unwelcome, why would I stay there? And when I say that I am talking about government because the ­people of the UK agree with me.”

Trump gave the exclusive interview with The Sun hours before Air Force One touched down at Stansted Airport at 2pm yesterday. Of his four-day visit, he added: “Many people are delighted. I get thousands of notifications from people in the UK that they love the President of the United States.”

He described a West London pub being renamed The Trump Arms for the duration of the trip as “wonderful”, adding: “I love those people. Those are my people."

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The bombshell interview will not only empower Brexiteers, but will likely lead to a further deterioration in relations between the two nations. According to Axios, "this is literally the exact opposite of what the Brits were hoping for from this trip. They were eager to improve the relationship between Theresa May and Donald Trump. They were hoping for support from Trump — and a signal to voters that there’s a positive road ahead with May’s Brexit plan. They wanted Trump to talk up the possibility of a U.S.-Britain bilateral trade deal. In this interview he trashes that idea, rubbishes her approach to negotiating Brexit, and props up her political nemesis and future leadership rival Boris Johnson."

Then again, Trump being Trump, perhaps what the people really expected was precisely this: another shock from the US president, who yesterday almost left Angela Merkel in tears during his NATO summit.

In other details, as covered by the Sun, Trump:

Accused EU leaders of destroying its culture and identity by allowing in millions of migrants

Tore into London Mayor Sadiq Khan for not standing up to terrorists

Blamed Khan for spiralling crime in the capital

Insisted former Foreign Secretary Boris Johnson would make “a great Prime Minister”.

Denied once branding Theresa May a “bossy schoolteacher”

Maintained he would keep ties with Russian tyrant Vladimir Putin despite the Salisbury Novichok poisonings

Demanded Britain and other Nato countries spend more on defence

Spoke of his sadness at feeling unwelcome in the capital by anti-Trump protesters

Claimed millions of Brits backed his policies

Told of his pride at taking wife Melania to meet the Queen

The full interview can be found at this link