In the grounds of a derelict school in Wrexham there’s a small, makeshift camp that appears to have been imported from the apocalypse.

Among the abandoned shopping trolleys, empty vodka bottles and piles of discarded clothes, several men and two women stumble around on a windy, grey afternoon, apparently oblivious to their surroundings. One man plays, childlike, with a bicycle wheel, but the others hardly move. They stand outside their tents, shaking their heads, shuffling back and forth, their eyes staring way off into the distance. They all have their reasons for being there, but one thing unites them: they all use spice, the “zombie drug” – so called because of the way it almost instantly reduces users to a semi-comatose state.

Few drugs have achieved such notoriety in so little time. A synthetic substance that emerged only three years ago has already wreaked chaos within the prison service and placed huge pressures on the emergency services. In every town centre, spice users can be found begging for the small amount of loose change they need to buy their next fix.

Ministers and harm-reduction experts clash over what could, or should, be done as the crisis shows no signs of abating. The latest statistics confirmed last week that deaths from synthetic drugs, of which spice is the most notorious, are on the rise.

And Wrexham has found itself at the sharp end of this trend. A few months ago, pictures of spice users slumped unconscious in the town’s bus station went viral on social media. “Zombie hunting” became a Facebook pastime.

“We’ve been dealing with spice for two years, but it’s only in the last six months that it’s become a real problem,”says Rowena Gregor, a case manager with the Wrexham branch of Arch, an organisation that helps rehabilitate drug addicts. “It’s all down to social media. All towns have a spice problem, but in the smaller towns it tends to be concentrated in one area – in this case around the bus station. Everyone was getting off and on the buses and seeing it.”

As Wrexham’s problems attracted national attention, complaints were made about the number of spice users congregating outside the town’s drop-in centres. Then, three weeks ago, amid the furore, one was forced to temporarily close its doors, leaving the users with nowhere to go. Hence the camp.

Spice was sold legally in ‘headshops’ but has now been banned. Photograph: David Sillitoe/The Guardian

Luke Roberts has been at the camp for a couple of weeks. He started using spice after the cot death of his five-week-old daughter Eva-Rose two years ago. “I’m not saying I was an angel before, you know, but it helps,” Roberts said. He has the face of someone who looks both older and younger than his 37 years.

A former heroin addict, he pays £25 for a 7g bag of spice – also known as mamba – which will last him a day. “I beg, borrow or steal the money. I shoplift. I get my benefits as well. I can’t resist it. It’s got me hooked so much now. But if you want to come off it there’s no detox programme.”

Spice started life as a “legal high” – a laboratory-engineered chemical that claimed to mimic the effects of cannabis and which came to national prominence around three years ago. Combined with dried plant matter, the drug was sold in “headshops” which promised that when smoked it delivered a herbal high. But this was a seductive lie.

“This is not cannabis; it is not naturally occurring,” said Dr Oliver Sutcliffe, senior lecturer in psychopharmaceutical chemistry at Manchester Metropolitan University. “The chemicals in spice are manufactured in a lab. They don’t get formed in a plant.”

The chemicals are called synthetic cannabinoid receptor agonists (SCRAs). Because they have an effect on many of the body’s cells, not just the brain, they were originally developed by pharmaceutical firms to help understand how putative new drugs could be used to treat different conditions.

But the SCRAs produced unwelcome side-effects and the drug giants discontinued their research. For many years they were forgotten, the blueprints for their manufacture lying idle in university archives.

“Since the internet, the access to information has become a lot easier,” Sutcliffe said. “The individuals manufacturing the chemicals are trawling the literature to make new products for the market. But because these were discontinued, a lot of the understanding of how these work in the body is not fully understood.”

Even the term “spice” is confusing. Originally it was just a brand name for one of the many of the legal highs or new psychoactive drugs on the market.

But soon it became the generic term for all of them, an elision that masks the often wildly different toxicity and potency levels associated with the different strains of spice circulating on the market at any one time. Recognition brought notoriety. A once obscure drug started showing up in presentations to hospital.

In 2015, when spice emerged from the shadows, new psychoactive substances were involved in 204 deaths in the UK, an increase of 25% from 163 deaths in 2014. But the deaths tell only part of the story.

“It destroys families, not just the individual,” said Linda Rogers, an area manager with Arch. “It destroys communities. We’ve had people who’ve worked most of their lives and are now addicted to this for one reason or another – because of stress, relationship break-ups, the loss of a job.”

Gregor estimates that 45% of her clients have a spice problem. But the drug now consumes a disproportionate amount of her time and resources.

“There are three times as many people [with problems other than spice] who need our help,” Gregor said. “It’s unfortunate that this group has shut down services for others to access. It’s the reaction to it; it’s completely instant. You only need a couple of drags and you’re gone. Because they collapse, members of the public think they need an ambulance. But what we’re finding now is people are getting complacent and thinking ‘oh it’s a spice overdose’. There have been a couple of occasions when it’s been a heroin overdose and there’s been a delay in administering the right response.”

Growing public alarm about the threat posed by legal highs led the government to introduce the Psychoactive Substances Act last year. The legislation not only banned their sale, but introduced the prospect of a seven-year prison sentence for offenders. It delivered almost immediate results.

Prohibited from selling spice, their main earner, many of the headshops – the retailers that sell drug paraphernalia – called it a day. This time last year, three months after the ban was introduced, government figures confirmed that 332 retailers had stopped selling psychoactive substances. Surveys suggest that usage of the drug has declined correspondingly – the latest Crime Survey for England and Wales estimates that the use of new psychoactive substances has fallen from 0.7% of those surveyed to 0.4%

“Among festivalgoers and clubbers there’s absolutely no interest in it,” said Fiona Measham, professor of criminology at the University of Durham. “It’s not a drug that is popular among young adults. Under 1% will say they’ve tried it.” But post-ban, the drug continues to devastate the lives of two of society’s most vulnerable – and ignored – groups who don’t show up in the official figures: the street homeless and prisoners, with membership of one group often conferring membership of the other.

“Spice really started being used in 2013,” said Martin Blakebrough, chief executive of Kaleidoscope, an organisation that runs several drug treatment services in Wales. “If you trace a map of drugs across England, you’ll find that where there’s a prison population, that’s where it has been introduced into the wider community.”

Paul Matthews, 28, earned the nickname “Splash” because he stole koi carp to feed his cocaine addiction – an addiction that finally brought him a prison sentence.

Now with support from Arch, which helps former addicts recover their sense of self worth through volunteering and team-building exercises, he is rebuilding his life.

Taking a break from a team litter-picking exercise, he shook his head at the memory of what spice had done to fellow inmates. “It’s worse than heroin. I’ve seen people who haven’t had it for days coughing up blood. It’s a killer. Four people on my wing died from it.”

The Wrexham homeless camp – the town has a growing problem with use of the drug. Photograph: Howard Barlow/The Observer

Measham, who sits on the government’s Advisory Council on the Misuse of Drugs (ACMD), teaches in prisons, where the number of deaths linked to new psychoactive substances has risen to at least 79 since June 2013, when the count was started. “I’ve been told by the inmates that there are a small number of people who will deliberately be arrested so that they can smuggle in spice,” she said. “It’s worth them getting arrested and getting a short sentence because of the amount of money they can make from it.”

Especially now. Since the ban, prices have gone up, doubling or quadrupling in some areas. But the inflation is tolerated. Spice still delivers a big bang for your buck. Whereas a gram of cannabis will make around four joints, a gram of spice can make triple this.

The price hike reflects the role that street dealers are now playing in the illicit spice market. “Whereas they (spice users) could go to the headshops and know what they are buying, now it’s a dealer’s paradise,” Rogers said.

Professor David Nutt, the former chair of the ACMD, who was forced out of the post after repeatedly clashing with ministers over drugs policy, believes the ban has simply driven the spice market underground.

“It was about gesture politics, to appease some rightwing Tory MPs,” Nutt said.

For dealers, prohibition meant another new drug for them to push. “Online you can buy a gram or two grams of the pure chemical, the cannabinoid, for about £2,” Sutcliffe said. “That will make 100g of spice. Divide that up into half-a-gram bags: 200 bags at £5 each, that’s a grand.”

Some of the chemicals will be impounded in transit. “But even if only 10% of the chemicals get through, you can see the economics for criminal gangs. They’re looking at this and thinking, this is a no-brainer.”

Currently the chemicals are imported from China and, to a lesser extent, India. But Sutcliffe believes a domestic production line could emerge one day. “The chemistry is very straightforward. You would not need a great deal of expertise. There’s no evidence that there are any manufacturing facilities in the UK, but it would be naive to ignore the potential for them.”

Rick Bradley, operations manager at the drug treatment charity, Addaction, is based in Kent which, prior to the ban, had more headshops than anywhere else in the country.

“You’ve now got a market that’s in the hands of the criminal fraternity,” Bradley said. “Headshops were comparatively safe. You weren’t going to go into one and get mugged; it was a transaction like anywhere else on the high street. Now young people go to street dealers and this brings additional risks of what the products might be mixed with on the street, the risks around mugging, drug debts, sexual exploitation.”

How significantly the risks have altered post-ban is debatable. Sutcliffe is one of the few chemists who tests spice seized by police. Using gas chromatography–mass spectrometry he examines batches of the drug to determine the best harm-reduction strategies for the health and emergency services.

Since the ban, Sutcliffe has analysed batches that have been found to contain the chemical AMB-FUBINACA at higher concentrations than that which caused the hospitalisation of 18 people in Brooklyn last year. He’s also found strains of spice containing the cannabinoid 5F-ADB which has been linked to at least 10 fatalities in Japan. More recently he has discovered crystalline forms of the drug. Last week, Wrexham drug services were warned that a batch of LSD that had been dipped in spice was in circulation in the town.

Sutcliffe has found that samples of spice seized in prison are more “blended” than those sold on the street. “It’s worrying,” he said. “If you’ve got two or three different cannabinoids present you do not know how those chemicals are going to interact. The pharmacology of how these things work in the body is not understood when they are being used in their single forms – but when you throw multiple compounds into the mix, the risks go significantly up. It becomes even more unpredictable.”

Users report blacking out, memory lapses and chronic stomach pains, as well as heart palpitations, shivers and sweats. “Spice works in a similar way in the brain to the active ingredient in cannabis that makes people stoned–the chemical THC,” explained Celia Morgan, professor of psychopharmacology at the University of Exeter. “But where THC partially activates the brain’s cannabinoid or CB1 receptors in your brain, spice fully activates them. This means that they have very different effects. Spice and other synthetic cannabinoids are considerably more potent than cannabis. And their effects are so wide-ranging and potentially damaging because the CB1 receptors that these synthetic drugs have been designed to target are common in many different regions across the brain. The memory effects are likely to come from the density of CB1 receptors in the hippocampus – the temporal lobe may be why these drugs can cause seizures, and their dangerous cardiac, respiratory and gastrointensinal effects are likely to be due to the number of CB1 receptors in the brain stem.”

Measham knows drug workers who believe that spice is worse than heroin in terms of physical addiction. “Part of this is the way it creeps up on people. They thought it was a synthetic cannabinoid, which makes it sound benign. All sorts of people were trying it, putting the same amount in a spliff as they would if it was cannabis, but it could be 100 times more potent.”

Bradley has no doubts that spice is addictive. “What you wouldn’t get from smoking standard cannabis is a physical dependency. But it’s hard to deny now that some people will get a physical dependency [from using spice] that is more akin to an opiate user.”

So how is the problem of spice tackled in other countries? Do bans work? Prior to the UK ban, the only two countries in the world to have passed similar legislation were Ireland and Poland, which both subsequently saw increases in the use of new psychoactive drugs.

Nutt said that the history of drug control over the last century proves that prohibition does not work.

“When they banned opium, people started injecting heroin; when they crunched down on cocaine, people started using crack. It’s much harder to close a door than it is to open it.”

Martin Powell, campaigns manager at Transform, a thinktank that pushes for drugs liberalisation, suggested that what was happening in Wrexham would, in time, spread to other regions.

Spice is known as the ‘zombie drug’ because of the effect it has on the user. Photograph: Joel Goodman/LNP/Rex/Shutterstock

“If there is a financial incentive for it to happen in one place it will happen elsewhere as well.”

Arfon Jones, the North Wales police and crime commissioner, whose patch includes Wrexham, believes the spice problem has been exacerbated by the ban. “I’ve called for the regulation of drugs ever since I’ve been in office,” he said. “The local media run polls that suggest there is 70% support for it. The positive sentiment on social media is also very high. There’s a sea change among the people of this country; they realise the war on drugs is not achieving much. I think the Home Office are behind the times in understanding this change in attitude.”

Powell draws comparisons with other countries. “The Netherlands don’t have a spice problem. It’s never developed there. People just stuck with using cannabis. You can’t wish away the problem we have now, but if we did legalise cannabis we could be reasonably confident that we would reduce the number of new users who might have moved into these products if cannabis wasn’t available.”

Nutt agrees. “I’d have a legal cannabis market – that would almost instantly destroy both the skunk and the spice market. Personally, I think prisoners should be allowed to smoke cannabis. None of them would use spice then, almost certainly. Instead people would have access to low-strength traditional cannabis with a nice THC ratio. It would dramatically reduce the use of more harmful cannabinoids.”

But spice users like those living in the makeshift camp in Wrexham are unlikely to be able to afford cannabis. Powell concedes the point – “which is why we’re calling for some regulated availability of less dangerous spice variants”.

Measham wants the government to adopt a licensing regime modelled on New Zealand’s psychoactive substances act, which has yet to become law. Under the proposals, manufacturers assessed as producing low-harm psychoactive substances would be allowed to sell the drugs under licence.

“We had a window of missed opportunity when the new psychoactive substances problem emerged,” Measham said. “Responsible retailers found themselves threatened by organised crime and the tabloids who chased them and made them out to be the problem. So they got out.”

But despite the chaos that spice has brought to the prison, police, health and emergency services, it still remains largely a criminal justice issue, rather than a medical emergency.

“We know there are antidotes to spice but they’ve been shelved by the drug companies,” Nutt said. “I find it frustrating that when people are dying from Ebola there’s an initiative to stop that, but when people are dying from spice the government says it’s not our job. It should commission someone to get an antidote back into the medical arena.” But this is unlikely to be made a priority any time soon.

Josie Smith, head of the substance misuse programme at Public Health Wales, oversees Wedinos, the Welsh Emerging Drugs & Identification of Novel Substances project, which spots new types of drugs often months ahead of the criminal justice system.

Since the ban, Wedinos has detected fewer variants of spice on the market. But those that are in circulation, Smith says, are “considerably more toxic and dangerous”. And she has noticed another trend, too. “When it was available in head shops, we saw a lot more use among younger people. That’s not being reported to us any more.”

Instead, more than a year on from when the government took action against a substance it warned could “devastate lives,” spice, once relatively uniform when it was legal and attractive to experimenting teenagers, has become a wildly unpredictable drug explicitly targeted at some of the most vulnerable groups.

A zombie drug has created a zombie army, shunting those on the margins so far to the edge of society that they are seen more as ghouls than people.

“We’ve got to remember these people are human,” Gregor said. “They’re people’s mums and dads and brothers and sisters and when they’re posted all over Facebook, their families are seeing that and that’s shaming for them. And that just makes them want to use more.”