The last time Barron Trump was at the US Capitol for a presidential swearing-in he was ten years old, wearing an ill-fitting shirt with a crumpled collar and looking like he'd rather be anywhere else in the world.

He was barely acknowledged by anyone, least of all his older siblings, who studiously ignored him as they waited frosty-faced along with everyone else for their father to arrive and be inaugurated as the 45th President.

His mother Melania then spent the next eight years doing her utmost to ensure people kept on ignoring her son, as she fiercely protected his privacy to the point that when he turned 18 and it emerged that he was 6ft 9in tall it came as a huge shock to almost everyone.

Monday's second inauguration of his father provided a salutary lesson in the quirks of fate because, seemingly without even trying, Barron Trump has eclipsed all his brothers and sisters as – literally – the standout star of the Trump family.

And it appears that even if he never asked for this, he's quickly adapting to his new status.

When his father addressed a 20,000-strong arena crowd at his post-inauguration rally, he did what he always does nowadays and singled out Barron to stand up and introduce himself.

Trump joked: 'And then I have a very tall son named Barron. Has anyone ever heard of him?'

Trump Senior proudly turned to the young man sitting behind him who, with his slicked-back hair and elongated black-clad frame, looked not dissimilar to Hollywood's idea of a Mafia hitman.

Barron rose to acknowledge what has become the obligatory wild standing ovation from Trump supporters – far louder and more sustained than for any other Trump family members bar his father – with surprising insouciance.

Barely smiling, he languidly went through each of his father's favourite rally gestures – punching the air, giving the thumbs up, pointing at random people in the crowd and putting his hand to his ear to encourage them to scream louder – while the audience roared approval.

They did the same every time Barron's face appeared on the giant video screens.

What explains the rock star status of Barron Trump in the Make America Great Again world?

His father obviously helps considerably, bigging him up at every opportunity. On this occasion he reminded everyone that Barron 'knew the youth vote' and had advised him to go on edgy podcasts presented by the likes of outspoken commentator Joe Rogan, thereby helping to win Trump the support of young male voters. 'He understood the market,' said Trump of his son.

And yet it was hardly rocket science to work out that Trump should target the hugely popular and conservative Rogan, who has more than 14 million listeners – Trump insiders whisper that their boss has rather over-egged his youngest child's importance to their election victory.

Some believe that Trump principally keeps showering praise on Barron to please Melania who, despite whatever faults she may have in the eyes of Democrats, is clearly a devoted mother, and was beaming with delight when Barron took the applause on Monday.

Others note that, superficial as it may sound, Trump admits that he likes to surround himself with attractive people and that Barron, who has inherited Melania's looks, is rather better looking than the other Trump male offspring Donald Junior, 47, and Eric, 41.

He's also, as insiders of the Trump camp have attested, rather more personable than his siblings. He displayed that at the inauguration ceremony when, seemingly alone among them, he made a point of going over to shake hands with their father's political betes noires Joe Biden and Kamala Harris.

He's also got a sense of humour, sneaking up behind a group that included his half-sisters Ivanka and Tiffany and sister-in-law Lara Trump to photobomb them moments before the inauguration.

Quietly self-assured, though not 19 till March, Barron was given pride of place next to the rather excitable Elon Musk during the swearing-in ceremony.

During the day he was also seen chatting animatedly with Amazon founder Jeff Bezos and, over a congressional lunch, with powerful Republican Senator Tom Cotton and Pete Hegseth, Trump's nominee for Defence Secretary.

Barron's tailor (yes, he has one already) Nathan Pearce, who made him a set of bespoke suits in the run-up to the inauguration, called him not only 'super-bright' but 'hilarious' and able to hold his own in a room of top businessmen.

'He can talk to them all day because he's witty, smart and has a dry sense of humour,' he gushed.

It's easy to forget Barron only left school a few months ago and is so fresh into public life he doesn't yet have his own Wikipedia page.

As a student at New York University, where he is in the first year of a business degree and arrives and leaves each day surrounded by a swarm of Secret Service bodyguards, there have yet to be any reports of high-handed, entitled behaviour that one might expect of a Trump scion.

'We're not hearing anything bad about him, which suggests he's keeping his head down,' a fellow student told The Mail on Sunday. Some young female students reportedly find him attractive, but given that he doesn't spend much time on campus they're getting little opportunity to talk to him.

'He loves his classes and his professors,' said his mother in a recent interview. 'He's doing well, he's thriving and he's enjoying being in New York city again.'

His father has said of Barron: 'He's always been a very good student – he's smart.'

However, Melania also admitted that Barron was aware that he was hardly experiencing the usual student lifestyle. 'I don't think it's possible for him to be a normal student,' she said.

He is certainly not a normal student. For all the effort that his mother put into raising him away from the Trump family maelstrom (they spent much of their time with Melania's Slovenian parents – father Viktor and her late mother Amalija, after they moved to the US in 2017) Barron is already following in Trump's business footsteps.

A few days ago it was revealed that he had started a luxury property company with two business-minded young friends last summer. The Trumps have always been intently focused on making money, but this showed unusual commitment to the cause, even from a young man who as a child liked to dress in a business suit.

Trump, Fulcher & Roxburgh Capital, which was set up in July, just two days after his father was almost assassinated by a gunman at a rally in Pennsylvania, was a partnership with a classmate at Barron's £32,000-a-year Palm Beach, Florida, school and with a Republican Congressman's cousin. 

Its founders said that they aimed to focus on 'high end' projects, including golf courses and expensive properties in Utah, Arizona and Idaho. However, the company was dissolved only four months later, in November.

Cameron Roxburgh, Barron's business partner, told Newsweek that they had wound up the enterprise to avoid media attention when Trump was re-elected President – but added that it might be relaunched this spring.

Roxburgh, who was at school with Barron, said that the President – who inherited his father Fred's New York property empire – offered his son business advice but not funding, adding that they hoped the venture would eventually be incorporated as a subsidiary of the Trump Organisation.

The business's principal office is listed at Trump's Mar-a-Lago estate in Palm Beach but it was incorporated in the state of Wyoming, which is considered particularly business-friendly thanks to its low taxes and minimal regulations.

According to his father, Barron has also played an instrumental role in educating him about cryptocurrencies such as Bitcoin, a scandal-plagued industry that Trump previously dismissed as a 'scam' but which he has now controversially embraced.

In September, Trump set up a crypto company called World Liberty Financial, which Barron partly owns and is listed as the business's 'DeFi visionary' – a reference to a branch of crypto known as decentralised finance.

If he finds his version of student life somewhat unfulfilling and making money far more attractive, Barron may yet drop out of university early (particularly as US degrees last four years).

There's already speculation that Trump – who can no longer count on the services in government of daughter Ivanka and her husband Jared Kushner – might persuade him to do exactly that so he can help him in the White House.

Melania has hitherto been seen as a block on that. When Barron was chosen as a Florida delegate to last summer's Republican National Convention, she 'regretfully' declined on his behalf, citing other commitments.

But as the adulation last week illustrates, many Trumpites, and especially those who want to see Trump Senior establish a family dynasty, continue to regard Barron as 'the future' and live in hope that he will take the plunge into politics sooner rather than later.

On social media, Barron-mania sees him compared to Alexander the Great and Augustus Caesar. On eBay, you can buy badges bearing the slogan 'Barron Trump President 2044'.

It may not be too long before his father is wearing one too.