Dr Ash Kapoor is nearly 60 but, by his reckoning, he has an awful lot more to look forward to.

Another 63 years, to be precise. None of which will be spent lolling about in a care home waiting for lunch and praying for a peaceful departure in his sleep.

No, the second half of Ash's life promises to be even better than the first.

He is expecting to enjoy fantastically high energy levels and do an awful lot of barefoot walking in nature and immersing himself in ice baths.

He'll be disappointed if he's not doing chin-ups well into his 80s and swimming in Alpine lakes for another half century. And sporting his fantastic head of thick and lustrous hair, for a long time yet.

And if things go to plan, he'll even - and I'm not sure if I should whisper this or shout it from the rooftops - be both sexually enthusiastic and extremely active, well into his 100s.

Because Dr Ash, a pioneer in regenerative medicine and founder of the Levitas Clinic, is not interested in just existing - 'like those sad, grey people you see just sitting, on their screens, waiting to die'.

No, he's talking about living with what he calls, 'full independence, purpose and in pursuit of fulfilment' - really contributing to society, right up to the end.

The eclectic mix of treatments, costing £3,000, included a facial massage

'Of course the idea of living to 123 is realistic. Totally realistic!' he says, in his lovely soft voice with perfect cadence and diction. 'And so that is our target.'

Well, wow and how fantastic - if quite a recalibration for those of us in our 50s to suddenly discover that there is far more life ahead, than behind.

Even better, it turns out that the secret of living to 123 is surprisingly simple and straightforward.

Because it involves no dictator-style organ transplants - as discussed excitedly by Russian President Vladimir Putin and China's Xi Jinping when they met at a military parade in Beijing earlier this month, both hoping to live to 150.

And no need to live like Bryan Johnson, the American longevity obsessive and tech millionaire, who spends $2million a year trying to reverse his biological age. He eats only green mush and is constantly hungry, never exposes his bluey green skin to sunlight, goes to bed at tea time and has forgotten how to have fun.

Even better, there is no need to spend the billions that Elon Musk, Jeff Bezos and other Silicon Valley tech bros have been splurging into biochemical cell regenerative research in an attempt to extend their lives.

No. Living longer the Levitas way involves a simple 90-day programme of cleaning out, repairing, renewing and resetting our bodies to their natural state - as if we were living in the wilderness like Masai warriors - free from modern day toxins that bombard us.

After which, Dr Ash says, we could all be disease free. Now and in the future.

Jane was given a state-of-the-art tooth clean to protect against periodontal gum disease

'Inflammation is the cause of every disease - all 126,000 of them,' he says, adding if we remove inflammation from the body, we remove illness. 'Genes are not your destiny,' he says. 'You can change the outcome.'

So what about a predisposition to dementia? 'Don't worry about it,' says Dr Ash. Rheumatoid arthritis. Colitis. High blood pressure. Alzheimer's. Auto immune disease. Diabetes. Joint inflammation?

'Not a problem,' says Dr Ash. 'It's like pressing "Control, Alt, Delete" on the body. We can reset everything.'

All of which sounds, well, almost too good to be true.

As does the price. Because Dr Ash insists that it does not cost the millions lots of his patients would happily spend to extend their lives. But a few thousand pounds for the initial 90-day programme. (In extremis, I could apparently buy some herbs from Holland & Barratt and do a DIY version, though it would take longer.)

Dr Ash has had success. You might remember the articles in this paper, written by TV journalist Donal MacIntyre, who lost more than three stone - and kept it off - during a 23-day fast under Dr Ash's supervision earlier this year.

Afterwards, 58-year-old Donal said he felt like a man reborn. His blood pressure normalised, he stopped being pre-diabetic and no longer needed knee surgery.

Of course, Donal was obese (17-and-a-half stone) and anyone who loses that much weight is likely to have a new spring in their step.

Jane in a body balance suit to improve circulation and blood flow

But many of Dr Ash's patients are not remotely fat.

Some are high net worth individuals in their 60s experiencing burnout. Others have lost their vim and verve. Some just want to embrace a new way.

To see what all the fuss is about, I visit the Levitas clinic in Mayfair, London, to try the 'specialist consultation', which is the starting point for all Dr Ash's new patients.

It is an eclectic mix of treatments (costing £3,000), which includes light therapy, shockwave therapy 'like acupuncture on steroids', facial massage, body balance, in a big blue compression suit, and a state-of-the-art tooth clean to protect against periodontal gum disease, which has been linked to Alzheimer's.

There is also a strange hair rejuvenation session in which a serum made from trout sperm is injected into my follicles because, according to Dr Ash, 'hair loss is just a sign that your body is defeated'. The serum helps nudge the follicles back into life.

But it all starts with a body composition test - 'we turn you inside out' - which involves standing on a monitor and holding two spindly paddles as it measures fat composition, muscle structure, sugar levels, etc.

But most important is the body's ketone count, which gauges our ability to metabolise 'internal fat larders' into energy. This process of the body feeding off itself is called 'autophagy'. It reduces inflammation and the likelihood of disease - and is key to Dr Ash's programme.

And here, my results make him very excitable indeed. Because, yes, I need to lose four kilos (9lbs) of fat and my organs are pretty much coddled in lard, but my muscle mass, or internal scaffolding, is 'excellent'.

Face therapist Pelin Saray gave Jane a number of different facial treatments

Most importantly, my body is already ketonic - busily raiding its own larders.

'This is a great start! You are very, very lucky,' he says. 'You'd be a very quick fix.'

Which would involve seven weeks of taking a blend of premium Australian herbs (such as psyllium husk) to detox the 'hideous debris' in my small intestine. Then a detox of my liver to fix my natural energy. Then a three-day fast (water only). Followed by seven days with one small meal a day. After which he'd rebuild me with peptides (amino acids that do wonders for everything from skin care to hormone regulation) and get me going on breathwork and ice baths.

'A little bit of work and you could change everything. You'd cruise though. Everything will feel better,' he says. 'You'll sleep like a baby, immediately add 20 years to your lifespan. And you'll be nicer to be around.'

It turns out that all Dr Ash's patients are nicer after their reset. 'It shifts them from the materialistic side of their brain to the community side,' he says. 'Releases them from their ego.'

As I mull over whether I could eke my pension out over another 20 years, we move to the next stage.

An anti-inflammatory drip containing turmeric (a known anti-inflammatory), which goes into my right arm and makes me feel a bit sick and weird and worried I'll bleed yellow in the future.

But kind Dr Ash takes my mind off it by gently massaging my arm and telling me how he believes the prevalence of ADHD is all about our failure to metabolise the stored sugar in our bodies.

Dr Ash Kapoor and technician Manny put the turmeric drip into Jane's arm

How, unlike Bryan Johnson - who he says looks gaunt and is very arrogant - he drinks alcohol. Though he does eat just one meal a day - often a light vegetable curry - in the evening and gets up at 4.30am. And, most surprisingly, how he has never taken a drug in his life - not even paracetamol - and has no truck with prostate screening tests, because 'it's all just inflammation' and he'd be alert to any changes in his body.

'Don't let the doubt come into your head!' he says.

When the drip is finally empty, we move on to the next treatment, where he injects carbon dioxide into my eye sockets - yes, really - causing my eyes to swell up so much that I can't open them for the next five minutes. Apparently, this will make the bags under them look better for at least three weeks.

And as I lie there in the dark, he tells me that, as an NHS GP in Hampshire, he became so depressed prescribing drugs to endless chronically ill oldies with hypertension and arthritis, that he felt there must be a better way.

Which is why he started exploring how to live better and longer, the natural way. To that end, he attended courses on epigenetics, peptides, longevity and regeneratives in the US and Europe, and set up Levitas ten years ago - and now has a top-of-the-range silver Bentley complete with personalised number plate and driver.

Because his approach to health and longevity has taken off like a rocket. Partly because, he says, it works. And not just for the 90 days, but far beyond, like Donal, who went on losing weight after his fast. Because our brains are rebooted, too.

'People become addicted to feeling well,' he says. 'They start reading up. They change their behaviour.'

They take up breathwork and ice baths and ditch gyms and start walking around parks in their bare feet, happily eat just one meal a day in return for being happier. And they will eulogise to anyone who'll listen about their personal transformation.

Which means that most of his patients are word of mouth.

'Many are high net-worth individuals who run half the world. Well-known people. Others are just not getting any joy out of life,' he says. 'But everyone is fixable.'

Some are also surprisingly young. 'We've got 30-year-olds who are depleted internally through anxiety, stress and disease,' he says. 'And I've got an 80-year-old gentleman who does 20 chin-ups a day and swims in a lake and is busy opening up a new business and doing podcasts. He no longer sees his age.'

But, of course, he still looks it.

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Which is where all the bio regenerative aesthetic treatments come in - such as hair rejuvenation with stem cell boosters.

Because one of the problems is that - how to put it delicately - some parts down below stop working if they're left unused for too long.

'I've got lots of 80-year-old men coming in saying, "I need to get sorted out!" ' he says. 'They've let things lapse, they've normalised decline.'

So through a process he calls 'sexual optimisation', he draws their blood and centrifuges it to extract the growth factor, the naturally-occurring active ingredient which can stimulate cell growth. Which is then injected into the blood vessel of the penis and, hey presto! - back on the horse. And, just in case anyone's wondering, he can do the same for the clitoral area, increasing the sensitivity by jump starting it with growth factor, should an 80, 90 or 100-year-old lady so require.

Gosh, it's a lot to take in and extremely tiring, what with Dr Ash's extraordinary energy levels and a day spent with all those needles stuck into my arms, eyes and hair follicles.

But as we bid goodbye, as he gives me a big, strong, life-affirming hug and sends me on my way, I start to ponder.

Could I ever justify the expense, or, for that matter, starve myself for three days? And perhaps more importantly, would I even want to live to 123, when most of my family and friends most certainly will not be around? Still, I wouldn't mind just another 20 years.

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