Life has changed somewhat for Amir Khan since 2004 when he became a national treasure, cheered on by his Pakistan-born born father famously adorned in a Union Jack waistcoat.

There have been ups and downs - quite literally - picking himself up from the floor quite a few times in a pro career which reached its pinnacle as a two-time world champion.

Not bad for a lad I got to know quite well in Athens and beyond, covering the majority of his 39 fights and attending his wedding.

During his run-up to the Olympic final, which he lost narrowly to the great Cuban Mario Kindelan, then the world’s number one amateur, Khan sought my advice on how to deal with the escalating media interest. I told him: "Just be yourself."

I had first seen his lightning-fast skills in a schoolboy championship in Barnsley where it was obvious that here was a young superstar in the making.

Now, at 34, King Khan is among the wealthiest personalities in British sport, said to be worth upwards of £23 million ($32 million/€27 million). And although he claims he has not yet officially retired he has just embarked on a new BBC TV reality show Meet the Khans: Big in Bolton - a sort of a British version of the United States' Keeping Up With the Kardashians.

More than anything the eight-part documentary series highlights his luxury living in the Lancashire mill town of Bolton. The boxer, his wife of seven years, Faryal Makhdoom, an American heiress from Manhattan, and their three young children.

Quite staggering to see how the boy from Bolton unashamedly splashes the cash. His run-around is a blood-red Lamborghini and there is a Rolls-Royce in the garage for use on special occasions. He tells how he has been stopped several times by the police when driving it, hardly surprising these days, but you can bet the boys in blue obsequiously seek his autograph and request selfies once they recognise him.

Amir’s lifestyle reminds me that several of the sports personalities I knew from humble beginnings are now high on the very rich list, having gone from grassroots to greatness.

Among them is entrepreneur and former athlete Alan Pascoe, who admitted to me when I ghosted his book that when he married wife Della he did not have two half-pennies to rub together - actually just £11 ($15/€13) in the bank. Towards the end of his career on the track as a Commonwealth Games gold and Olympic silver medallist hurdler, he borrowed £3,000 (/€) from an athletics benefactor and started a sports PR company that he eventually sold for £15 million ($21 million/€18 million) and now lives in an imposing Thames-side mansion, close to my own rather more modest residence.

Then there is a certain Lord Sebastian Coe, who, as plain Seb, a 17-year-old junior 800 metres champion, I invited to a Sports Writers Awards dinner in London. As an impecunious student from Sheffield he could not afford overnight accommodation, so he stayed in our spare bedroom. I eagerly await a return invitation to his rather chic pad overlooking the main drag and casino in Monte Carlo, where he reigns these days as Il Supremo of World Athletics.

Like Khan and Pascoe, he is a multimillionaire - and good luck to them and they’ve earned it with hard work, sweat, occasional tears and in Khan’s case quite a lot of blood, as he points out in the documentary.

"The way I look at it [his lifestyle] is that I work very hard for it," he says. "I’m always one punch away from getting hurt so I like to treat myself or treat my wife. But I do respect money and that’s one of the reasons I do a lot of charity work as well.

"Recently I started to go to orphanages in Africa and when you see how people live there, you realise how fortunate we are. That gave me a wake-up call."

It is certainly true that Khan shows huge largesse with his charity world in the UK and Pakistan, and has opened a state-of-the-art gym in Bolton that is free to use for underprivileged youngsters.

Even so, I’m not sure that the exposure of such opulence will enhance Khan’s image, especially in a northern town which is one of the hardest hit in Britain by the deprivations felt by the coronavirus, with much unemployment and closures of shops and businesses.

I doubt whether so much flaunting of wealth, like buying a £30,000 ($41,000/€35,000) Rolex for his child’s first birthday, or hiring a yacht to cruise around the shores of Dubai as a lavish birthday present for his wife, will go down too easily with less well-off Boltonians.

Nor the building of luxury wedding venue for the wealthy which he says admits has gone £7 million ($10 million/€8 million) over budget.

In the first episode of Meet The Khans, aired on Monday evening, Amir is then seen in a conversation with his wife about the project's finances.

He says: "I was told it would cost £3.2 million ($4.4 million/€3.8 million), it's now cost about £11.5 million ($15.9 million/€13.5 million).

"It hurts you knowing how much money has gone to waste, you're talking millions. I'm talking £5 million ($6.9 million/€5.9 million) has literally gone missing."

Faryal replies: "I know, it's sad, really sad."

Persuading Faryal to help him to get the wedding venue back on track, Amir tells her: "You are a bit more ruthless. You can say no to people, whereas I tell them it's ok they can have it for free.

"We need you in charge of that side to make sure we don't spend too much money.”

The pair's relationship hasn’t always been smooth. Since marrying in 2013, they have had their various squabbles - mainly the boxer’s admitted infidelities - splashed cross the tabloids and their lifestyle is is often regarded as gaudy or inappropriate. At one stage they split up for six months and the philandering Amir falsely accused his wife of having an affair with Olympic and world heavyweight boxing champion Anthony Joshua. It turned out the pair had never even met.

But Amir vows he has "grown up", amended his ways and has been forgiven his much-publicised transgressions. All seems to be well with them now and the series is fairly light-hearted and fun - which is what reality shows are bout.

In it, Amir and Faryal explain why they wanted to make Meet the Khans, where their relationship stands now and why they still love living in Bolton.

"I’ve watched a lot of these reality TV shows and I like them because it gets to the real person, what they’re really about, what they’re really like," says Amir. "A show will help us to engage with our fans and give them a chance to see the real side of us."

Faryal adds: "We wanted to capture our life and Bolton and being parents, making decisions at work. We’re just young, fun parents juggling small children. We want to be relatable, you know.

"It’s not up to us to tell people what to think, but in the show we’re completely honest. We can’t really apologise for who we are. We’re going to be our real selves, whether anyone likes it or not.

"Because on Instagram I never smile, everyone’s always like, 'she’s so serious, she looks so rude'. But I’m quite warm and just your typical American girl. I love being a mum and I’m a businesswoman as well."

Their ranch-style home is palatial and they seem to have so much money they do not know what to do with it, but Khan, who says he wants two more fights before he finally quits boxing, insists he will always be that boy from Bolton. "We’ve had so many opportunities to leave. We were looking at a house in London and then to buy a holiday home in Dubai. But something always brings me back to Bolton.

"My career started off here and the love I get from the community makes it very hard for me to leave. I’ve got a boxing academy here where I’m teaching kids boxing - we’ve created world champions and Olympians. And then I’ve got my huge wedding hall project. I like giving back to the community, so I want to stay here and help people.

"I think making his documentary has brought us closer and made us realise how much we need one another. We obviously have three children now which makes us even closer. Everyone has ups and downs, but we just want to look forward now."