The Queen and US President Donald Trump and First Lady Melania have met at Windsor Castle.
The American leader will be treated to a Guard of Honour at the historic royal residence in Berkshire and will also join the British monarch for tea in the castle
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Mr Trump spoke of his admiration for the Queen in his interview with the Sun, in which he called her a “tremendous woman”.
He told the paper: “If you think of it, for so many years she has represented her country, she has really never made a mistake. You don’t see, like, anything embarrassing. She is just an incredible woman.
“My wife is a tremendous fan of hers. She has got a great and beautiful grace about her.”
Mr Trump and First Lady Melania Trump will meet Britain’s head of state at the dais in the castle’s Quadrangle, which features a neatly manicured central lawn.
Located in the Upper Ward, it sits with the castle’s famous Round Tower to its west, and is surrounded by the impressive state, visitor and private apartments.
A Guard of Honour, formed of the Coldstream Guards, will give a Royal Salute and the US national anthem will be played.
The Queen and Mr Trump will inspect the Guard of Honour before watching the military march past.
Mr and Mrs Trump will then take tea with the Queen in the castle.
Update - 3.45pm: Trump backtracks on earlier criticism, calls May an ‘incredible woman’
Donald Trump has heaped praise on “incredible” Theresa May and hailed UK-US relations as the “highest level of special” hours after incendiary comments criticising her premiership.
After intensive talks at Chequers in the wake of an interview in which he said the UK Prime Minister’s Brexit plans would kill off a trade deal with America, the US president told Mrs May “whatever you do is OK with me” but urged her to “make sure we can trade together”.
President Trump Participates in a Joint Press Conference with the Prime Minister of the UK https://t.co/2bVIKMLlr4— The White House 45 Archived (@WhiteHouse45) July 13, 2018
Protesters gathered in central London to denounce the visit for stoking “division along fault lines of fear and hatred”, including a Mayo man selling Trump toilet paper.
But well away from the noisy demonstrations, Mr Trump and Mrs May took questions from reporters.
The president said Mrs May “can’t walk away” from exit talks with the European Union, though suggested she could use other methods to secure a good deal.
But he praised Mrs May as a “very tough negotiator” and described her as an “incredible woman” who is “doing a fantastic job”.
The US president left Mrs May badly wounded when he criticised her negotiating style, lavished praise on Boris Johnson and attacked her Brexit plan in an interview with The Sun.
He apologised to the PM for the story and said the newspaper left out the good things he had said about her, adding “it’s called fake news”.
Mr Trump said: “She’s a very smart, very tough, very capable person and I would much rather have her as my friend than my enemy, that I can tell you.”
Update 3.30pm:Protesters gather ahead of Trump's meeting with Queen in Windsor
Anti-Donald Trump protesters have sympathised with the Queen for having to host the US president for tea at Windsor Castle.
While London had the Trump blimp, Windsor saw demonstrators holding a sea of colourful placards with one saying: “Beware Ma’am He’s a Sociopath”.
Around a hundred protesters gathered close to the walls of Windsor Castle hoping to catch a glimpse of the president when he arrives later and make their feelings known.
Jenni Collins, 36, said: “It’s important to show up and show that we’re upset we’re engaging with Trump, and have put him on this level of pomp and ceremony.
“I especially feel for the poor old Queen having to have him to tea.”
Holding a homemade placard which said “Equality Diversity No Trump For Tea!” she added: “It’s the level of lies and distortion he puts out of his mouth and is picked up and taken as truth I find most disturbing, and obviously his stance against diversity, equality, racism and immigration.”
The police presence within Windsor has grown steadily through the day with officers wearing high visibility jackets stood in prominent positions and armed police patrolling the streets.
Earlier a police boat was spotted patrolling the nearby River Thames while the banks of the waterway opposite the castle was searched.
She also had a royal-themed placard which read “Off With His Head”, the 40-year-old added: “I think it would have been a very bold move not to get him over here, because we rely on the US for trade.
“But I’m glad it’s not a full state visit because he doesn’t deserve that level of care, I thought Blenheim Place was a bit over the top, I also feel sorry for the Queen because she’s got to meet him.”
Update 3pm: Trump says relationship between US and UK 'indispensable'
Donald Trump and Theresa May have held a joint press conference at Chequers this afternoon.
Update - 1.40pm: Trump hails 'very strong' relationship with May despite earlier criticism
Donald Trump insisted his relationship with Theresa May was "very, very strong" just hours after leaving the UK Prime Minister humiliated with an explosive assessment of her leadership.
The US president left Mrs May badly wounded when he criticised her negotiating style, lavished praise on Boris Johnson days after he walked out of Cabinet and warned her Brexit plan could "kill" any UK-US trade deal.
Speaking at Chequers, as the shockwaves continued to reverberate following his brutal assessment, Mr Trump insisted said he and Theresa May had "probably never developed a better relationship" than during the dinner last night.
Seated alongside the UK PM at her official country residence in Buckinghamshire, Mr Trump appeared to adopt a more conciliatory tone, saying: "The relationship is very, very strong, we really have a very good relationship."
"The relationship is very, very strong." US president Donald Trump talks of his bond with Prime Minister Theresa May ahead of their meeting at Chequers. https://t.co/KWYQGUcVpZ pic.twitter.com/qbjYi6IzLq— ITV News (@itvnews) July 13, 2018
He added: "We had a dinner where I think we probably never developed a better relationship than last night. We spoke for an hour or an hour and a half and it was really something."
The UK PM and the US President arrived by helicopter at Chequers after a visit to the Royal Military Academy Sandhurst and will now be locked in hours of talks which will culminate in what promises to be an awkward press conference.
Mrs May said trade would be discussed during the meeting.
"We are going to be discussing the special relationship, which is great, between the UK and US," she said.
"We are going to be discussing the real opportunities we have got to have this trade deal coming up when we leave the European Union.
"And of course, we will discuss foreign policy and defence and security issues, where we work really closely together with the US."
In an explosive interview with The Sun, Mr Trump said he would have carried out the Brexit negotiations "much differently" and claimed the UK Prime Minister did not listen to his advice.
He said: "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.
"If they do that, then their trade deal with the US will probably not be made."
He went on to say Mr Johnson, who quit as Foreign Secretary over the Chequers plan, was "a great representative for your country".
Asked if he could become prime minister he added: "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."
As he sat down with the PM at Chequers before a row of British and American flags, the President rolled his eyes when reporters asked if he regretted what he said in the interview.
The trade deal warning sparked a sterling sell off, with the pound shedding 0.6% against the dollar to trade at 1.31.
Labour leader Jeremy Corbyn said: "Theresa May has invited President Trump to our country at a time when his dangerous and inhumane policies are putting the lives and wellbeing of millions of people at risk."
Protesters took to the streets in London to demonstrate against the president's visit - and in Parliament Square, a Trump baby blimp was raised up in the air.
Former Labour leader Ed Miliband said he is taking part in protests because the US President's politics are "profoundly dangerous".
London mayor Sadiq Khan said he would not rise to Mr Trump's "beastly" comments, after the president attacked him over the wave of terror atrocities and said he was doing "a terrible job".
Mr Trump will head off to meet the Queen, who he called a "tremendous woman", at Windsor Castle after talks at Chequers wrap up.
Meanwhile, First Lady Melania Trump played bowls with the Prime Minister's husband.
Mrs Trump, 48, joined Philip May, 60, at the Royal Hospital Chelsea in London where she met Chelsea pensioners and local children.
First Lady Melania Trump has met schoolchildren and played bowls at the Royal Hospital Chelsea during #TrumpVisitUK— Sky News (@SkyNews) July 13, 2018
Follow live updates on the President's visit: https://t.co/99rHHKY4a7 pic.twitter.com/DQYwupZpHa
Earlier: Donald Trump arrives for Chequers talks hours after humiliating Theresa May
Donald Trump has arrived for talks with Theresa May just hours after lobbing a political grenade that has left the UK Prime Minister badly wounded.
The US president humiliated Mrs May by criticising her approach to negotiations, lavishing praise on Boris Johnson days after he walked out of her Cabinet and warning her Brexit plan could “kill” any UK-US trade deal.
Mr Trump’s comments emerged as Mrs May pulled out all the stops to entertain the president and wife Melania with an evening of pomp and ceremony at Blenheim Palace.
Where are your manners, Mr President?— Sam Gyimah (@SamGyimah) July 13, 2018
The PM and the president will now be locked in hours of talks at Chequers that will culminate in what promises to be an awkward press conference at her country residence.
Two ministers broke cover to make their displeasure at Mr Trump’s comments known.
Education minister Sam Gyimah said: “Where are your manners, Mr President?”
Culture minister Margot James tweeted: “No Mr President @POTUS Boris Johnson would make a terrible PM.”
Mr Trump sent shockwaves through Westminster when he gave an explosive interview to The Sun where he said he would have carried out Brexit negotiations “much differently” and claimed the Prime Minister did not listen to his advice.
He said: “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.
“If they do that, then their trade deal with the US will probably not be made.”
But Mr Trump appeared to link Brexit to the current trade dispute between the US and EU over steel and aluminium.
No Mr President @POTUS Boris Johnson would make a terrible PM— Margot James (@margot_james_) July 13, 2018
He told The Sun Mrs May’s plan would affect trade “unfortunately in a negative way”. He added: “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.”
Asked if he could become prime minister, he added: “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.”
In a statement following the publication of the Sun interview, the White House press secretary said Mr Trump “likes and respects Prime Minister May very much” and he “never said anything bad about her”.