The pair elbow-bumped and strolled on the promenade in Cornwall earlier, and as the leaders sat down for talks, Mr Biden told journalists he had joked to Mr Johnson that they both ‘married way above our stations’.
As well as taking the lead in cracking gags, Mr Biden also appeared the far more confident of the two premiers, with his commanding posture and a series of authoritative gestures.
This included a ‘power pat’ at one stage, where the President placed the flat of his hand on the back of the Prime Minister.
Darren Stanton, TV’s Human Lie Detector and leading body language expert told MailOnline: ‘The significance of placing a hand on the back of someone else and guiding them along is a pure submissive gesture, and is meant to convey the message ‘I am more powerful than you’.
‘President Biden seems very comfortable in his own skin and typically presidential in his posture and the way in which he moves. He is quite a tall thin man and takes large strides.
‘It was interesting to see Boris, who is shorter, and takes less [large] strides keeping up with him.’
President Biden shows off his ‘power pat’, after placing the flat of his hand on the back of the Prime Minister
As well as taking the lead in cracking gags, Mr Biden also appeared the far more confident of the two premiers, with his commanding posture and a series of authoritative gestures
The cheery appearances came in spite of a row over Brexit today, as the White House tried to put out the flames of a major transatlantic bust-up.
Brexiteer Tories had branded the 78-year-old Democrat ‘senile’ after he failed to side with the UK in its ‘sausage war’ bust-up with the EU, and the US President used his diplomats to express ‘great concern’ over the conflict.
Earlier in the day, the two leaders, along with their wives, Jill and Carrie, strolled along Carbis Bay.
Mr Stanton said their respective behaviours in this environment told a story of who was really holding the power in the much-trumpeted ‘Special Relationship’.
‘The initial footage where the four walked towards the view of the ocean is probably the most telling of all interactions that we have been able to see so far,’ he said.
‘Upon walking to the sea, Boris continues to make this rather odd hand gesture as if he is guiding President Biden.
‘However it’s clear he is not aware of [what the plan is] by asking an aide shortly after.
‘When we are in a position of authority and feel confident there is a classic gesture of placing our hands behind our backs.
‘We often see police officers do it, military personnel CEOs of companies and other authoritative figures.
‘This is an unconscious gesture of exposing the stomach and torso, we feel confident enough to psychologically expose some of our most vulnerable organs.’
The expert pointed out that Mr Johnson putting his hands in his pockets was perhaps another suggestion of submission.
‘When the two men are looking at an exhibition, Boris again adopts a similar sequence of postures where he does not know what to do with his hands,’ he said.
‘The whole thing ends up looking like he is fidgeting.
‘Overall I think Biden found the experience within his stride and was consistent with being presidential and confident, whilst Boris was less so.’
Newlywed Carrie Johnson cut an elegant figure in a scarlet £325 LK Bennett gown as she made her debut onto the world stage alongside her husband Boris today