EXCLUSIVEHow the world's frozen billionaires will avoid being resurrected poor: Their severed heads are pumped with 'anti-freeze' and brains put on ice. Now they have a way to beat their biggest fear...

In Ancient Egypt pharaohs were mummified so their bodies would be in perfect condition for their journey into the afterlife. And, defying the old adage that 'you can't take it with you when you go', a decent chunk of their worldly possessions were placed in the tomb with them.

Thousands of years later, the 21st century's pharaohs are 'cryonicists' - people with the money and determination to live again by being frozen after death, in the hope that one day science will be advanced to the point that they can be revived.

Cryonics is turning into a multi-million pound industry in which people are routinely paying at least $200,000 (£155,000) to have their bodies frozen on top of $100 (£78) monthly storage fees, which could theoretically stretch into eternity. And participants are being urged to consider exactly how they hope to live if they do ever wake up - and how they might pay for it.

Up to four bodies can be stored in each 'dewar' or vacuum flask at the Alcor (An American cryonics pioneer) facility in Arizona

Up to four bodies can be stored in each 'dewar' or vacuum flask at the Alcor (An American cryonics pioneer) facility in Arizona 

After all, what's the point of being resurrected in the year 2524 at one of the secluded cryonics storage facilities around the world with no money for even the most basic essentials? Or worse, imagine returning as simply a disembodied brain (an increasingly popular option) and not being able to afford to be put into a beautiful new body?

To address these sort of nightmare scenarios a new species of lawyer - the 'revival trust' specialist - is now available.

Much like other trusts, they are essentially a legal agreement, whereby you give your assets to someone else so they can manage them for the benefit of a named beneficiary. Revival trusts name the deep-frozen corpses (or brains) as the beneficiary, treating them, for legal purposes, as unborn descendants.

Even without the huge uncertainty of what the law will be in a few centuries' time, it's more than a little complicated. And yet, say the experts, it's the only way. Leave your money in a bank account and it will simply be divided up among your beneficiaries. Turn it into gold and bury it deep in the ground in a place only you know, and there's no guarantee that your new self - which could be a clone, cyborg or your decapitated head wired up to a computer - will remember anything about it.

An estimated 5,500 people, including hundreds in Britain, have reportedly signed up to be frozen after they die and defrosted when a cure for whatever killed them has been discovered - and possibly when scientists have found a way of making bodies young again.

Remains are kept at -196C by liquid nitrogen that has to be topped up occasionally due to evaporation

Remains are kept at -196C by liquid nitrogen that has to be topped up occasionally due to evaporation

There are currently four cryonics storage facilities worldwide: two in the US, another in Berlin and a fourth, which might be a riskier option, in Moscow.

Many aspiring cryonicists - such as the three Oxford University dons who signed up with US cryonics companies 2013 - are not especially rich. But others who are reportedly on board - including British TV star Simon Cowell, Silicon Valley billionaire Peter Thiel and the late US casino mogul Don Laughlin CHK (not to forget Britney Spears and Paris Hilton who have both expressed interest) - have considerable fortunes that they'll want to draw on if they are ever brought back from oblivion.

The 1,500 or so members of Alcor (an American cryonics pioneer) wear medical alert bracelets while they're still alive that tell hospitals and doctors to contact the company in the event of the wearer suffering a life-threatening emergency.

Although it's commonly described as 'freezing', technically the process they undergo is 'vitrification', in which the water in the body is turned into a glass-like state rather than ice, because the latter expands and so tends to burst open cells and tissues.

If any would-be cryonicist dies, an Alcor team is on standby to rush to their bedside. (Some members even move close to Alcor's Arizona facility to cut the response time as much as possible).

The team will restore the client's breathing and blood circulation with a mechanical heart-lung resuscitator used in CPR and known as a 'thumper', and then inject anti-coagulants to keep the blood flowing. This is all done in order to protect the brain from damage, which can occur if it goes too long without oxygen.

Next, the body is cooled in an ice water bath and the blood is drained and replaced with a medical-grade antifreeze.

When it reaches the Alcor facility, if the patient has chosen to preserve only their brain, surgeons perform a 'neuro-separation', removing the head at the sixth cervical vertebra and pump more anti-freeze into the severed head. A forensic pathologist opens the skull and removes the brain.

Whatever – entire body or brain – is being preserved for posterity, it goes into a 'dewar', a giant insulated vacuum flask which contains no electricity but which is instead kept at -196C by liquid nitrogen, which has to be topped up very occasionally due to evaporation.

Alcor's Patient Care Bay is currently home to about 230 patients, some of them pets, stored in 'Bigfoot' dewars that each accommodate four whole-body patients and five 'neuropatients', commonly known as brains. Cryonicists insist that in these conditions, the bodies and brains can remain unaffected by decay indefinitely.

Returning to life in the body of someone in their 80s or 90s rather defeats the object of the exercise for many clients and so they're increasingly opting to be decapitated. Storing a brain is cheaper (Alcor charges just over £60,000), quicker and – cryonics experts claim – more socially acceptable given anatomy departments and research institutes have been storing brains for years.

And while other body parts can be recreated, each brain is unique. There's also a widespread belief that any future society that can revive a brain will also have worked out how to create a new body to put it in. Cryonicists have various ideas – all of them purely theoretical - about what to do with a thawed-out brain, including connecting it up to 3D-printed organs made from human cells, creating clones using DNA from the brain, and giving the brain a robotic body.

It's important to emphasise that no human brain or body has yet been revived after death and the science - sceptics insist it is merely a 'pseudoscience' - of cryonics remains a huge shot in the dark. In the cryonics world, estimates of how long it might take before it's scientifically possible vary from 40 years to more than a thousand.

However, as enthusiasts - who include respected doctors and scientists - will chorus in response, it's 'the next best thing to being dead forever'.

Maybe, maybe not, but those willing to take the plunge into the liquid nitrogen are swiftly made aware that it's a little more complicated than signing on the dotted line with a company like Alcor and keeping fingers crossed (assuming they still have any) that science will one day catch up with their dreams.

Late US casino mogul Don Laughlin was reportedly on board with cryonics

Late US casino mogul Don Laughlin was reportedly on board with cryonics

Wealthy fans of the science, such as TV star Simon Cowell, have considerable fortunes that they'll want to draw on if they are ever brought back to life

Wealthy fans of the science, such as TV star Simon Cowell, have considerable fortunes that they'll want to draw on if they are ever brought back to life 

Many cryonicists have arranged for their freezing and storage costs to be paid out of life insurance policies that kick in when they die. But that's the bare minimum of what they're likely to need financially, especially given the distinct possibility that any future generation might want some sort of incentive to revive them beyond mere curiosity.

Meanwhile, futurists generally agree that by the time it's likely to be feasible, the skillsets of those being defrosted will be irrelevant to earning a living in the new world in which they find themselves. So coming back poor is likely to be tough.

'You'd have to be completely retrained so it would be a lot easier if you had just wealth,' says Mark House, an Arizona lawyer and revival trust specialist who advises some 100 Alcor members.

He told the Mail the idea of cryopreservation 'has gone from crackpot to merely eccentric' and so there's growing interest in how it might work.

His clients - including a handful in the UK - range from the moderately well-off to the seriously wealthy. Can they really stay rich forever? Well, possibly. In the US, an inheritance loophole called dynasty trusts already exists that is used by the super-wealthy to pass down their fortunes through multiple generations (while avoiding a 40 percent federal tax on estates worth more than £10.5 million). Even if they have a trust set up in America and are cryonically preserved there, UK residents have to pay a capital gains tax on their trust earnings every 10 years.

There are, however, significant hurdles. At present, for instance, there are rules designed to stop fortunes being hoarded in perpetuity so US states have varying limits on the maximum timespan of trusts.

Furthermore, trusts have to be administered by named trustees but, if its sole beneficiary is frozen in liquid nitrogen and technically dead, 'there's nothing to prevent the trustee from wandering off with the money,' House says. And even if they are honest, they will die eventually. The alternative is to appoint companies as trustees but few seem to want to take on that onerous responsibility.

Meanwhile, lawyers urge cryonics patients to be very specific about the circumstances under which they'd want to be revived.

Florida lawyer Peggy Hoyt, who advises dozens of cryonics enthusiasts, admits that many of her clients have surprisingly not given much thought to how they want to be revived - whether, for instance, they'd only consider coming back in the same body with their memory entirely intact or whether they'd be happy if their brain has been uploaded to a computer and they're an animation.

They will be lucky to come back in any shape or form, say sceptics. Nobel Prize-winning British-American biologist Venki Ramakrishnan identifies 'myriad' potential problems with cryonics. For a start, he says, even if the patient moved right next door to a cryonics facility, in the minutes or hours that elapsed between death and freezing, every cell in the dead person's body undergoes drastic biochemical changes due to lack of oxygen and nutrients.

The cryonics industry's preferred solution to this is to preserve only the brain, arguing that as long as its physical structure is intact, scientists can see the connections between all the billions of brain cells and so be able to reconstruct the person's entire brain. But this complex process, known as 'connectomics', is in its infancy. And besides, says Ramakrishnan, a brain without a body is no fun at all.

'The pleasures our brains derive are mostly of the flesh. A good meal. Climbing a mountain. Exercise. Sex,' he says. 'Moreover, if we wait until we age and die, we would be pickling an old, decrepit brain, not the finely tuned machine of a 25-year-old. What would be the point of preserving that brain?'

Naturally, none of this is going to convince those who believe that, when it comes to having a second chance at life, it's a case of nothing ventured, nothing gained.