Trump's unprecedented foray into UK politics

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 made quite clear that Washington had clear 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

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

Trump also comprehensively 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.

Trump notably chose to play down one area of contention with Britain -- by saying a solution could be found to address US concerns 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.