Trump was deeply complimentary towards Prime Minister Theresa May before she cedes power, pledged fealty to an alliance that shaped the modern world and chose not to publicly air political differences with Britain.

"I have greatly enjoyed working with you. You are a tremendous professional and a person that loves your country dearly," said Trump, who has vigorously criticized May's handling of Brexit.

His respectful approach pleased British officials who helped organize his trip and who had fretted about the unpredictable President's habit of detonating diplomatic grenades -- especially where the two sides differ on Iran policy, climate change, international institutions and the Middle East.

But the subtext of his wider remarks was clear. In the Trump administration, UK-US ties can only reach their full fruition if Britain makes political choices palatable to Trump and chooses leaders such as his friend, former London Mayor Boris Johnson

While most presidents go out of their way to avoid the appearance of interfering in the internal affairs of other countries, Trump rigid expectations of its old ally. Many presidents have developed closer personal and political friendships with British leaders. Others opposed certain British attitudes -- such as Franklin Roosevelt's hostility to the British Empire beloved by his friend Winston Churchill. And Barack Obama electrified British politics by declaring Britain would go "to the back of the queue" for a trade deal with the US if it left the EU.

But no American president has intervened as directly and unapologetically in recent years in British affairs as Trump.

Trump's snub

Photos: In pictures: President Trump in Europe US President Donald Trump, visiting the Normandy American Cemetery in France, participates in a ceremony to commemorate the 75th anniversary of D-Day on Thursday, June 6. Hide Caption 1 of 45 Photos: In pictures: President Trump in Europe Trump and his wife, Melania, visit the graves of troops who died on D-Day. Hide Caption 2 of 45 Photos: In pictures: President Trump in Europe The Trumps are joined by French President Emmanuel Macron and his wife, Brigitte, as they watch a flyover on June 6. Hide Caption 3 of 45 Photos: In pictures: President Trump in Europe A World War II veteran shows Trump a photo of himself with the President. Hide Caption 4 of 45 Photos: In pictures: President Trump in Europe Trump addresses the commemoration ceremony in France. Hide Caption 5 of 45 Photos: In pictures: President Trump in Europe Macron and Trump embrace during the D-Day ceremony. Hide Caption 6 of 45 Photos: In pictures: President Trump in Europe A World War II veteran looks over Trump's shoulder during the commemoration ceremony. Hide Caption 7 of 45 Photos: In pictures: President Trump in Europe At a D-Day event held Wednesday, June 5, in Portsmouth, England, Trump reads a prayer that President Franklin D. Roosevelt gave over the radio on D-Day. Hide Caption 8 of 45 Photos: In pictures: President Trump in Europe Trump heads back after speaking at the event in Portsmouth on June 5. Hide Caption 9 of 45 Photos: In pictures: President Trump in Europe Britain's Queen Elizabeth II and Prince Charles play host to the Trumps at the D-Day event in Portsmouth. British Prime Minister Theresa May is at left. Hide Caption 10 of 45 Photos: In pictures: President Trump in Europe Trump meets with German Chancellor Angela Merkel on the sidelines of the D-Day event in Portsmouth. Hide Caption 11 of 45 Photos: In pictures: President Trump in Europe The Trumps pose for a photo ahead of a dinner at Winfield House in London on Tuesday, June 4. Joining them, from left, are Woody Johnson, the US ambassador to the United Kingdom; Camilla, the Duchess of Cornwall; Prince Charles; and Johnson's wife, Suzanne Ircha. Hide Caption 12 of 45 Photos: In pictures: President Trump in Europe Trump and Prince Charles share a toast at Winfield House. Hide Caption 13 of 45 Photos: In pictures: President Trump in Europe Trump and British Prime Minister Theresa May speak at the dinner on June 4. Hide Caption 14 of 45 Photos: In pictures: President Trump in Europe Melania Trump spends time with Camilla and Suzanne Ircha, the wife of the US ambassador. Hide Caption 15 of 45 Photos: In pictures: President Trump in Europe Brexit Party leader Nigel Farage, center, arrives at Winfield House, where the Trumps are staying during their visit. Hide Caption 16 of 45 Photos: In pictures: President Trump in Europe Trump and May give a joint news conference on June 4. "I think she's done a very good job," Trump said, reversing past critiques of her failure to strike a Brexit deal that both Parliament and the EU can accept. Hide Caption 17 of 45 Photos: In pictures: President Trump in Europe Trump and May are followed by their spouses as they make their way to the news conference in London on June 4. The President offered plenty of praise for May, who recently announced her resignation. Hide Caption 18 of 45 Photos: In pictures: President Trump in Europe Philip May and Melania Trump attend a garden party at No. 10 Downing Street. Hide Caption 19 of 45 Photos: In pictures: President Trump in Europe Larry, the No. 10 Downing Street cat, sits underneath The Beast, the presidential armored Cadillac. Hide Caption 20 of 45 Photos: In pictures: President Trump in Europe Trump speaks opposite May at a business roundtable discussion in London. Hide Caption 21 of 45 Photos: In pictures: President Trump in Europe Trump stands next to Queen Elizabeth II before a state banquet at Buckingham Palace on Monday, June 3. Joining them are Melania Trump, Prince Charles and Camilla. Hide Caption 22 of 45 Photos: In pictures: President Trump in Europe The state banquet had a few hundred guests, including several of Trump's children. Hide Caption 23 of 45 Photos: In pictures: President Trump in Europe Trump and the Queen laugh during the state banquet. Hide Caption 24 of 45 Photos: In pictures: President Trump in Europe The Trumps tour Westminster Abbey on June 3. Hide Caption 25 of 45 Photos: In pictures: President Trump in Europe The President signed the guestbook at Westminster Abbey. "Thank you so much," his message said. "This has been a great honor. Special place." Hide Caption 26 of 45 Photos: In pictures: President Trump in Europe The Trumps are joined by Prince Andrew as they pay their respects at the Tomb of the Unknown Warrior in Westminster Abbey. Hide Caption 27 of 45 Photos: In pictures: President Trump in Europe The President's convoy drives down Pall Mall in London on June 3. Hide Caption 28 of 45 Photos: In pictures: President Trump in Europe Queen Elizabeth II welcomes the Trumps to Buckingham Palace. She took them on a tour of the royal collection. Hide Caption 29 of 45 Photos: In pictures: President Trump in Europe Among the items on display was "American Pewter Thoroughbred," a gift that Trump gave the Queen last year. Hide Caption 30 of 45 Photos: In pictures: President Trump in Europe Trump inspects a guard of honor at Buckingham Palace. Hide Caption 31 of 45 Photos: In pictures: President Trump in Europe The US National Anthem is played during a welcoming ceremony at Buckingham Palace. From left are Melania Trump, the Queen, Trump, Charles and Camilla. Hide Caption 32 of 45 Photos: In pictures: President Trump in Europe British Army troops fire a cannon in London's Green Park to mark the beginning of Trump's visit. Hide Caption 33 of 45 Photos: In pictures: President Trump in Europe The Queen greets the President as he arrives at Buckingham Palace. Hide Caption 34 of 45 Photos: In pictures: President Trump in Europe Prince Charles greets Trump as he steps off Marine One at Buckingham Palace. Hide Caption 35 of 45 Photos: In pictures: President Trump in Europe The Trumps are welcomed in London by Charles and Camilla. Hide Caption 36 of 45 Photos: In pictures: President Trump in Europe Trump's daughter Ivanka, who is also advisor to the President, looks out of a window at Buckingham Palace. Hide Caption 37 of 45 Photos: In pictures: President Trump in Europe People outside Buckingham Palace photograph the Changing of the Guard ahead of Trump's arrival on June 3. Hide Caption 38 of 45 Photos: In pictures: President Trump in Europe The Trumps arrive at Winfield House, the residence of the US ambassador, on June 3. Hide Caption 39 of 45 Photos: In pictures: President Trump in Europe Amnesty International installs "Resist Trump" banners on Vauxhall Bridge in London. Hide Caption 40 of 45 Photos: In pictures: President Trump in Europe Marine One flies past the BT Tower in London. Hide Caption 41 of 45 Photos: In pictures: President Trump in Europe The Trumps walk toward Marine One after arriving at London's Stansted Airport on June 3. Hide Caption 42 of 45 Photos: In pictures: President Trump in Europe The President salutes troops as he and the first lady arrive at Stansted Airport. Hide Caption 43 of 45 Photos: In pictures: President Trump in Europe Trump is greeted by UK Foreign Secretary Jeremy Hunt after arriving at the airport. Hide Caption 44 of 45 Photos: In pictures: President Trump in Europe The Trumps arrive at Stansted Airport. Hide Caption 45 of 45

Most notably, the President delivered a calculated snub to opposition Labour Party leader Jeremy Corbyn -- refusing to meet a man who lambasted him at a rally at the same time as he was meeting May.

"I don't know Jeremy Corbyn. Never met him. Never spoke to him," Trump said. "He wanted to meet today or tomorrow and I decided that I would not do that."

"I think that he is, from where I come from, somewhat of a negative force. I think that people should look to do things correctly, as opposed to criticize."

Corbyn's hostility to Trump, his policies and mainstream American foreign policy would shake relations between London and Washington should he ever reach 10 Downing Street.

Britain's paralyzing crisis over Brexit is so acute that it is not far-fetched to think Corbyn could be prime minister by the end of the year -- whoever wins the Tory election.

Corbyn, a long-time campaigner from the Labour Party's radical left wing, declined an invitation to attend a state banquet held by Queen Elizabeth II in honor of Trump Monday night. A Labour source confirmed he had however asked to meet Trump.

At an anti-Trump rally in London, the Labour leader lambasted Trump's brand of politics.

"I am not, absolutely not, refusing to meet anybody," Corbyn said, before speaking out forcibly for the rights of refugees, in a clear shot at Trump's policies on the US southern border.

"Don't treat them as enemies. Treat them as human beings and citizens of the planet who deserve out support, our sympathy and our understanding," Corbyn said.

Labour's foreign affairs spokesperson Emily Thornberry told CNN International Tuesday that her party's critiques were aimed at Trump and not America and were the dutiful warnings of a friend.

"He is dragging your country backwards," she said, explaining why Labour did not attend the state banquet. "It is wrong for you to be as racist as you are, it is wrong for you to be as misogynistic as you are. It is wrong for you to assault women. Why should we be afraid to say those things?"

Trump also used his news conference to take a fresh shot at London Mayor Sadiq Khan , who he blasted as a "stone cold loser" before landing in the UK on Monday.

"I don't think he should be criticizing a representative of the United States that can do so much good for the United Kingdom," he said.

Trump lays bets in PM race

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Trump also put all of America's chips on Conservative Party leaders vying to defeat May who want a comprehensive severing on US relations toward Europe.

The President will not meet the man who is his most favored candidate -- Boris Johnson, the former mayor -- on his trip, though did speak to him for 20 minutes by phone, a British official said.

Johnson, the Tory front-runner and flamboyant populist who draws comparisons to Trump, has been running a tightly controlled campaign. A meeting with the unpopular President may have served to scare away more moderate Conservative MPs.

"I know Boris. I like him. I've liked him for a long time," Trump said at a joint news conference with May, for whom Johnson has been a painful thorn in the side.

"I think he'd do a very good job," Trump said. The President also praised another top contender, Foreign Secretary Jeremy Hunt who was at the news conference.

But he stuck out a sharp elbow when asked about the prospects of Michael Gove, the current Environment Secretary and Johnson rival seen as less hardline on Europe than some candidates.

"I don't know Michael. But would he do a good job Jeremy?" Trump teased. In fact, Trump has met Gove, who interviewed him for the Times newspaper during a sabbatical from politics.

It was not immediately clear how the swipe at Gove would impact the Scottish-born Tory's campaign. But Trump's hardline views on Brexit connect with Conservative activists who will have the final say on the identity of Britain's next leader.

Tough terms on trade

Before he arrived in the UK on Monday, Trump had made another incendiary intervention in British politics -- calling on May to include Nigel Farage, whose Brexit Party triumphed in European elections, to be called into exit talks with Brussels.

The President welcomed Farage to a meeting at the US ambassador's residence in London on Tuesday.

"Good meeting with President Trump. He really believes in Brexit and is loving his trip to London," Farage wrote on Twitter after he emerged.

Trump notably chose to play down one area of contention with Britain -- by saying a solution could be found to address US worries that the involvement of China's Huawei in building a new 5G network could pose surveillance concerns.

He shrugged off a US warning that the crucial "Five Eyes" intelligence sharing agreement with the UK could be at risk.

"We're going to have absolutely an agreement on Huawei and everything else. We have an incredible intelligence relationship and we will be able to work out any differences," Trump said.

But when it came to the question of a future trade deal Britain would like to conclude with the US if it eventually exits the EU, Trump signaled that things could get contentious.

That includes access to Britain's fabled state-run National Health Service for American firms, a position that may be a deal breaker even for Trump-supporting Tories because it would involved partial privatization.

"I think everything with a trade deal is on the table. When you're dealing with trade, everything's on the table," Trump said. "So NHS, or anything else, or a lot more than that. But everything will be on the table, absolutely."

With those comments, Trump may also have made life more difficult for Conservative Party candidates he supports -- one of whom he would like to be soon dealing with as prime minister.