Before their first meetings with President Trump, world leaders were curious about which Trump would turn up at the negotiating table. Tim Stirzaker, director of a new BBC series, takes us through moments when the unconventional statesman revealed himself.
As Jean-Claude Juncker, former president of the European Commission, said to his chief of staff Martin Selmayr: "In politics you have to dance with the girls in the ballroom and he is now in the ballroom, so let's work it out."
Our goal for this series Trump Takes on the World was to get a behind-the-scenes view of Donald Trump's diplomacy, as told by those who were in the room at the critical moments.
We were able to interview some of Trump's top advisers as well as the foreign leaders and officials who clashed with him, and they tell us how the president's unique style left them stunned.
The first episode looks at how Trump fell out spectacularly with America's old allies in Europe.
'She couldn't take her hand back'
Theresa May was the first foreign leader to meet Trump face-to-face at the White House.
Her joint chief of staff, Fiona McLeod Hill, describes how the former prime minister reacted when Trump surprised her by holding her hand as they walked along the White House colonnade: "She felt she couldn't really take her hand back so she was stuck with the hand in the hand. And the first thing she said was 'I need to call Philip just to let him know that I've been holding hands with another man before it hits the media.'"
But before May could call home, Trump left the Brits further astonished by an outburst at lunch where he ripped into his own team for not putting through a call from Russian leader Vladimir Putin.
Thomas Shannon, acting Secretary of State, told us: "The president looked at the prime minister and said 'I don't believe this. Vladimir Putin is the only man in the world who can destroy the United States and I didn't take his call.'"
Find out more:
- The first episode of Trump Takes on the World airs on the BBC on 10 February
- It will be carried on BBC Two at 21:00 and repeated on Thursday at 23:30
- After the programme airs it can be watched on the BBC's iPlayer
A visit to Trump's 'SCIF'
Former Australian Prime Minister Malcolm Turnbull is another leader to get a taste of Trump breaking all the diplomatic rules.
At a G7 summit, Trump invited Turnbull and new French President Emmanuel Macron into his SCIF (a "sensitive compartmented information facility" normally reserved for highly sensitive meetings about national security).
Here, he starts to complain about a deal for the US to take a quota of refugees from Australia.
Turnbull says: "Donald said, 'Emmanuel do you know Malcolm has 2,000 of the worst terrorists in the world locked up on a desert island? And you know what's worse? Now I've got to take them.' And he turned to Emmanuel and he said, 'Emmanuel do you want to take them?' Macron had no idea what was going on, naturally, he was speechless."
'Do an interview on Fox News'
Former UK foreign secretary Jeremy Hunt discovered one way to get on the right side of Donald Trump.
Hunt had only been foreign secretary for a few days when Trump came to Britain for his first official visit. He told us: "I'd done an interview with Fox News, in which I defended the president's call for European countries to spend more on defence.
"He [Trump] came straight up to me, grabbed my hand and said 'Great interview on Fox News.' He said, 'I said to the people around me, I don't know who the hell that guy is but he's doing a great job.' And that was my first lesson as a diplomat: that if you want to get through to President Trump, do an interview on Fox News."
'Is Britain a nuclear power?'
During the same visit, Hunt wanted to make sure that when Trump met Vladimir Putin, he took a hard line with the Russian president - particularly in the wake of the Salisbury poisonings just a few months earlier.
John Bolton, Trump's national security adviser, told us: "My opposite number said: 'This was a chemical weapons attack on a nuclear power', to emphasise how significant it was. And Trump looked at Theresa May and said: 'Oh is Britain a nuclear power?' And I will say that the British stiff upper lips held but their eyes were wide as saucers."
When Trump does meet Putin in Helsinki, all the talk is of Russian interference in the US elections to help get Trump elected.
Fiona Hill - not Theresa May's chief of staff but Trump's top Russia adviser at the White House - remembers the extraordinary press conference as Trump suggested that he believed the Russian President over his own security services.
"My initial thought was just 'How can I end this?' I literally did have in my mind the idea of faking some kind of medical emergency and throwing myself backwards with a loud blood curdling scream into the media."
The first episode of Trump Takes on the World airs on BBC Two on 10 February