Angry-Baby Donald and Doting Donald

London: Friday July 13 will mark the day when the "special relationship" between the United States and the United Kingdom swung from one extreme to the other.

At one point, the relationship was sent into intensive care, grievously wounded, if not mortally hurt, by Trump's extraordinary attack on Theresa May and his suggestion that Boris Johnson "would be a great Prime Minister - I think he's got what it takes".

The President's exclusive interview in The Sun, described by The Guardian as a "verbal hand grenade", was considered so vicious and rude that even the Labour Opposition came to the aid of the British Prime Minister. Trump's remarks were the most biting any US President has ever made on visit to Britain.

However, at a joint news conference after his talks with May on Friday, Trump attempted to row back on the interview and lavished praise on the Prime Minister, contradicting his own withering assessment of her strategy publicised hours earlier.

Asked about that interview, Trump said he had not criticised May, describing her as "a terrific woman", who was smart, tough and capable.

"This incredible woman right here is doing a fantastic job, a great job," he said. "She's a total professional because when I saw her this morning, I said: 'I want to apologise, because I said such good things about you'. She said: 'Don't worry, it's only the press'." May, likewise, glossed over the comments in The Sun, saying her deal provided a platform for an ambitious free trade deal.

In the interview published just hours before he was due to have lunch with May and tea with Queen Elizabeth on Friday, Trump chided the "very unfortunate" results of the Prime Minister's Brexit negotiation.

"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," Trump told the Rupert Murdoch-owned Sun.

"I would have done it much differently," he told The Sun, which urged its readers to back Brexit before a referendum in June 2016. "I actually told Theresa May how to do it, but she didn't listen to me."

After a tumultuous week for May, when her Brexit secretary David Davis and foreign secretary Johnson resigned in protest at the Brexit plan, Trump heaped praise on Johnson, saying he "would be a great Prime Minister".

Questioned on Johnson's comments at a private dinner two weeks ago that Trump "would go in bloody hard" if he was negotiating Brexit, the President readily agreed: "He is right."

Even the shadow foreign secretary Emily Thornberry, no friend of the Prime Minister in normal circumstances, gave a remarkable defence of May, saying it had been "extraordinarily rude of Donald Trump to behave like this".

Thornberry said: "She is his host. What did his mother teach him? This is not the way you behave." Was Trump, who had been promised a full-fledged state visit by May when they met at the White House in January last year, seeking revenge because it had been downgraded to a "working visit"?

To be sure, Trump was given a guard of honour at Windsor Castle where he was taking tea with the Queen, and May put on a glittering dinner for the President and his wife Melania on Thursday night with a ceremonial welcome at Blenheim Palace, once the home of Winston Churchill, one of his great heroes.

But he was denied a stay at Buckingham Palace or Windsor Castle, and, to make red chilli to his wounds, a 20 foot high inflatable blimp caricaturing Trump as a whingeing nappy-clad baby clutching a mobile phone was successfully launched in Parliament Square on Friday accompanied by protests from an estimated 200,000 people against his visit.

Later, standing alongside him, May insisted: "We will do a trade deal with the US and others around the world.... The Chequers agreement reached last week provides the platform for Donald and me to agree an ambitious deal."

But the damage is done. The Daily Mail's page one headline on Friday read, "President's Brexit attack on May," while that in another Brexit support paper, The Daily Telegraph, was, "Trump: May's soft Brexit will kill chance of US trade deal."

The 28-minute interview with The Sun was conducted Tom Newton Dunn, the paper's political editor, at the US embassy in Brussels on Wednesday, ahead of the Nato summit.

When press secretary Sarah Huckabee Sanders announced the scheduled 10-minute slot was almost up, the President swiftly interjected: "No, give them a little bit more."

Why The Sun, a mass circulation paper once famed for its topless Page 3 girls?

The Guardian reckoned the interview was given to The Sun because it is "a Eurosceptic tabloid owned by Rupert Murdoch, whose Fox News channel supplies many of Trump's views".

Additional reporting by Reuters