When Prince Harry appeared on The Late Late Show, he showed a rarely seen side of himself.

He spoke candidly to James Corden on a range of uncomfortable topics and had fun rapping and dancing with the comic.

The interview was Harry's first since he stepped down as a royal, the Mirror reports.

In it, he even performed a rendition of the Fresh Prince of Bel-Air theme tune as he and James Corden visited the mansion where the Will Smith hit show was filmed.

The pair embarked on an open top bus tour where Harry spoke of his 'amazing' son Archie and his beloved wife 'Meg'.

But his warm disposition when talking about his young family seemed to change when he was asked about his grandmother Queen Elizabeth II and his brother Prince William, the Duke of Cambridge, according to a body language expert.

The Queen with Meghan and Harry during the 2019 Trooping the Colour parade

Judi James says that Harry becomes instantly protective and guarded when asked about The Queen.

When James Corden joked about playing William on the Netflix show The Crown, Harry becomes suddenly serious and his smile becomes a blank poker face.

Harry's strongest reaction came when he was speaking about 'stepping back, not down' from his duties in the UK, Judi says.

She noted that Harry appears dismissive and even 'sad' when speaking about his changed role.

Judi says of the 17-minute interview: "If this skit is representative of the kind of rules Harry prefers when handling the press and dealing with his own privacy, it would be very easy to see some confusing and possibly conflicting-looking messages.

"This is very much ‘celebrity’ Harry - or ‘Haz’ as we discover he likes to be called by ‘Meg’ - and the congruence or lack of it at certain points of his interview provide interesting clues about his levels of comfort and desire to be open, or the possible discomfort and desire for privacy.

"Waiting in the street to be ‘surprised’ by the arrival of the bus, Harry places his hands on his hips to create an air of confidence, and he even rolls his shoulders as though prepping for a physical fight.

"His first pose when sitting opposite Corden suggests some pre-interview anxiety as he performs a finger-pick ritual and seems to be leaning away from his host.

"But then comes the first moment of ‘confiding’ in Corden, telling him that he was ‘not allowed to’ go on open-top buses in the UK, and the way he pushes his chin out and drops his voice suggests the sense of restrictions in his life as a royal.

"Harry dresses like Corden and happily plays along with his host, showing what looks like a desire to perform as a celebrity in front of the camera.

"He even raps a bit before joining in the double-act comedy on a trip to the loo and even walks away from the two-man ‘sketch’ leaping and prancing like an excited kid.

"Meghan is clearly caught on the hop – not! – as we see her perfectly framed and lit and looking gorgeous on the phone screen.

"Harry stands in the background beaming with excited-looking love at his wife’s face and trying to get into shot like a man still besotted with his ‘Meg’ and possibly wishing she were there to help him out.

The Queen and Prince Harry during an engagement

"Haz’s hand gestures as he talks about meeting and dating Meg are expressive, emphatic and open.

"His use of illustrative movements suggest he is more than happy to tell the story of their first dates and how they fell in love.

"His legs are splayed to suggest confidence. He also, like any besotted dad, looks more than happy to talk about his ‘amazing’ son.

"When he speaks about Meg making waffles for Archie he acts out the actual gestures in a long mime, looking happy to share the daily experience and even mimicking his son’s voice at one point.

"Haz does begin to look more guarded when asked about the Netflix TV show The Crown. His hands come up in a more protective-looking barrier gesture and as they clutch in front of his chest he appears to be fiddling with his wedding ring, which is often seen as a self-comfort ritual that suggests a desire to be with your partner.

"When he goes on to speak about ‘My grandmother’ his arms also pull closer to his torso and he crosses one across his body in a partial barrier gestures.

"He tries what sounds like a verbal swerve but Corden pulls it back to the Queen and Haz is seen adopting another self-protective-looking pose known as the ‘Fig Leaf’.

"There is one point when the body language mood appears to change, when Corden suggests he (Corden) could be cast as William in The Crown.

"There is a pause before the camera moves to Haz’s face and suddenly he is in poker-face mode, with one elbow on the back of his seat and the hand part-covering a very serious facial expression.

"Harry’s eyes look away to the distance and although he makes a small joke his face is unsmiling at this point.

"Harry appears to want to make light of his new role in the royal family, though. Lolling in what looks like a relaxed pose he waves his hands in the air as he speaks and performs hand-twist gestures and thumb-jerks, seeming to want to diminish any idea of difficulty or challenge.

"Even when he says his aim is now to ‘Bring compassion, make people happy and try to change the world’ his relaxed hand gestures suggest he sees it as a task that should not be seen as difficult or daunting.

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"Harry’s quote about leaving the royal family: ‘Stepping back, not stepping down’, comes with some signals of discomfort though.

"He looks down in a cut-off as he shakes his head and rubs his hand down his thigh several times, suggesting what might be some sadder emotion.

"He uses some strong dismissive gestures when referring to the UK situation, though. ‘Whatever decisions are made on that side’ is said with a shake of the head as he stretches an arm out behind him in a pushing away gesture.

"The last scene involves an assault course challenge with James referring to Harry’s army experience before doing a comedy race. Harry clearly appears to not be haunted by the spectre of the infamous ‘Royal It’s A Knock-out’ at this point, standing with legs splayed in full alpha mode.

"It was an event like this that set the royal firm back a few years in the UK but Harry’s celebrity skills of humour appear more than up to the task in the US."