Nigel Farage has become the first British politician to meet Donald Trump since he became US president-elect.
The pair met at Trump Tower in New York and discussed "freedom and winning", according to Ukip sources.
The encounter will be seen as a major political coup for the interim leader of Ukip and came after he used the American media to warn Theresa May she needed to "mend fences" with Mr Trump.
Asked on Fox News why the president-elect should meet the PM after the things senior Tories had said about him, Mr Farage said: "I think he has got to meet her.
"Mrs May's team have been quite rude about Trump, so there are some fences to be mended.
"Trump is an Anglophile, he understands and recognises what our two great nations have done together between us. And, thank goodness, we are coming towards the end of an American president who loathed Britain.
"One of the things we can do, we can have between us a sensible trade relationship, cut tariffs, we are massive investors in each other's countries. There's a bright future."
Downing Street moved to try and play down the significance of the Ukip leader's meeting with Mr Trump.
A spokesman for Mrs May told the Press Association that No 10 "has been consistent that Mr Farage has no role" in the Government's relationship with the in-coming US administration.
The interim Ukip leader has suggested that "insulting" comments about Mr Trump by senior Tories may have been the reason why Mrs May was only 10th on the president-elect's list of foreign leaders to call after his surprise win last Tuesday.
Mr Farage's remarks came after it emerged Mrs May's two joint chiefs of staff had attacked Mr Trump on social media before taking up their current posts.
Fiona Hill posted last December: "Donald Trump is a chump", while her colleague Nick Timothy wrote in March: "American politics was depressing enough before Trump took off."
Foreign Secretary Boris Johnson was scathing about Mr Trump's attitude to Muslims while he was mayor of London last December, saying: "I think Donald Trump is clearly out of his mind if he thinks that's a sensible way to proceed, to ban people going to the United States in that way, or to any country.
"What he's doing is playing the game of the terrorists and those who seek to divide us. That's exactly the kind of reaction they hope to produce.
"I think he's betraying a quite stupefying ignorance that makes him frankly unfit to hold the office of President of the United States."
While pushing for a meeting between the president-elect and Mrs May, the interim Ukip leader appeared to make light of a now infamous 2005 videotape of Mr Trump in which he boasted about being able to grope women because of his celebrity.
"I will be encouraging him to make the UK his priority. I am now going to become a diplomat - 'Come and schmooze Theresa, don't touch her for goodness' sake'. If it comes to it I could be the responsible adult and make sure everything's okay," he told TalkRadio.
Only 15% of Britons think that Mr Trump will make a good president, according to a new poll.
Just over half of voters, 53%, believe he will do the most powerful job on Earth badly, the ComRes survey for The Sunday Mirror and The Independent reveals.
And 40% believe his occupancy of the White House will be bad news for Anglo-American relations, compared to 29% who think it will have a positive impact.
An overwhelming majority, 66%, believe Mr Trump will make the world a more dangerous place, with just 10% saying he will make things safer.