This rather damning assessment of both Rishi Sunak and Sir Keir Starmer - the UK's choice of future prime minister - focuses on their speech and body language, not how they might lead the country.

The leaders of the two main parties face weeks of interviews, speeches, and walkabouts as part of their general election campaigns.

Ahead of their first live TV debate, Sky News speaks to Paul Boross, a business psychologist and body language expert who has coached several politicians and celebrities, and Elizabeth McClelland, forensic voice, speech, and language analyst, about the gestures and verbal ticks that offer an insight into who the two frontrunners really are.

'They're no Obama - or Clinton'

First, we return to the accusation that neither the Conservative nor Labour leader are "blessed with natural charisma".

According to Mr Boross, neither Rishi Sunak nor Sir Keir Starmer "have that compelling, preacher-like rhythm to their voices", as former US Presidents Barack Obama and Bill Clinton do.

"In this general election we're not blessed with politicians who have that natural charisma - of an Obama or a Clinton," he tells Sky News. "They both struggle to build an authentic bond with the public."

By contrast, he credits both American leaders with using few filler words and being "very clear".

"If you watch them, they enjoy pausing and bringing people into the conversation. That's an art," he says.

Ms McClelland, who has decades of experience analysing speech for legal cases, says politicians' media training often makes it "difficult" to get an authentic idea of them.

But Mr Boross adds: "Although they'll be working very hard to reduce those weaknesses - their body language and speech patterns often reveal them."

Sunak: So fluent he barely blinks - speeding up under pressure

Having analysed Mr Sunak - both when making speeches and in interviews - Ms McClelland notes that he rarely pauses or uses filler words.

"He's a remarkably fluent speaker," she says. "He uses very few what we call pause phenomenon; he very seldom 'uhms' or 'uhs'."

This can be helpful, she adds, as it gives interviewers less opportunity to interrupt with a question.

She also draws on his former jobs in finance - and says: "He has a tendency to sound as though he's selling you a high-end financial product."

In terms of the sound of his voice, she describes it as "pure Westminster School, Oxbridge 'posh' with a contemporary twist" and "absolutely no reflection of his North Yorkshire constituency".

This is highlighted in his pronunciation of the vowels I and O, she says.

Commenting on his body language, she adds that he "seldom blinks" and has "learned to smile a lot and speak completely to the camera or person he's talking to."

Although his delivery is fluent, Mr Boross notes various ticks that reveal Mr Sunak's nervousness or discomfort.

Giving the example of being asked if he "caught pneumonia" after delivering his Downing Street election announcement in the rain, Mr Boross says Mr Sunak often responds with "nervous laughter".

"It's a very Rishi Sunak thing that when he feels confronted, he automatically bursts into nervous laughter," he says.

He warns that while it may appear friendly, the tendency to "over laugh" at things can come across as "awkward" or "inauthentic".

The prime minister also speeds up when under pressure, he adds. "When he's flustered his speaking pace increases."

With regards to body language, Mr Boross claims his facial muscles tighten and hands clench when he feels uncomfortable.

Although he uses few filler words, the ones he does opt for are "right and "look", which Mr Boross warns are too "short and sharp".

"He uses shorter, sharper ones to try and get on the front foot in interviews, but it comes across a little too tetchy".

"It makes him seem like psychologically he's already in opposition," he adds.

"He practically interrupts people when he says 'right', which can allow a slight air of superiority to manifest".

Starmer: 'Lawyer-ly' over-caution with too many 'uhms'

Sir Keir Starmer's previous job as a barrister still dictates the way he speaks, according to the experts.

While Ms McClelland describes him as "serious", Mr Boross says he is "over-cautious" with "controlled gestures".

"His lawyer-ly tone can be a bit over-cautious, and while precise, it can seem overly formal and lacking in spontaneity and emotional engagement," Mr Boross says.

This also comes through in his body language, he adds, via a furrowed brow and "frequently looking worried or stressed".

Both experts note he says 'uhm' and 'uh' far more often than his rival.

While in a legal context, McClelland claims this can be an indicator someone is lying, she says it can be a "purely innocent" feature of processing.

"Being a lawyer, he likes to think before he speaks, therefore I think he wants to be sure he's expressing himself lucidly and sincerely," she says.

Mr Boross argues it makes him sound less confident, however.

"When I've worked with politicians, it's one of the first things I eradicate from their speech, because it kills the message and makes them sound unsure."

He adds that Sir Keir's use of other fillers such as "right?" and "you know?" have the same effect, and suggest he needs reassurance around what he is saying.

While Mr Sunak appears to be making a concerted effort to sound more southern with his accent, Ms McClelland claims his Labour rival is doing the opposite.

"One thing I note with great interest is Starmer's efforts to emphasise his northern credentials," she says.

Drawing a comparison with former Labour prime minister Harold Wilson, she claims Sir Keir's pronunciation of his L and A sounds are not in line with his Surrey upbringing, Oxford education, and north London parliamentary seat.

While Mr Sunak appears "more relaxed" in front of a camera, Ms McClelland sees more sincerity in Sir Keir's style.

"I think you get more of a sense of the man behind the media image than you do with Sunak," she says.

And Mr Boross adds, that although still less fluent, Sir Keir is "loosening up" and has demonstrated a "better and faster" arc of improvement than his rival.