This article originally appeared on VICE UK.

"My whole house stunk of weed when I got home one day, so I accused my son of smoking it in his room. I was on the verge of kicking him out," says Sheila Marsden, a shop assistant in Downham Market, Norfolk. "A few days later, I heard some grannies in town whispering about the smell from the cannabis factory up the road in Wissington, and I had to go home and eat a slice of humble pie."

Most people don't know the British government allows cannabis to be grown on an industrial scale, never mind the fact that the UK is the world's largest exporter of medicinal weed products. For residents of Downham Market—a sleepy east Anglian town that was overpowered by a dank aroma this time last year—it's old news.

"The smell was so bad it was giving me headaches," recalls Marsden. "It reeked."

Baffled locals searched for the source of the stench for days, sparking a local mystery that worked its way into the national press. Some believed it was manure, others were convinced it was onions, some thought it was fertilizer—but one theory soon gained consensus, before an "odor consultant" confirmed the smell was indeed that of weed.

Downham Market

Seven miles away from the historic market town, within a monolithic industrial complex, sits the biggest weed greenhouse in Britain. Last year, its owners, British Sugar, stopped growing tomatoes in the 18-hectare [44-acre] greenhouse and quietly began producing cannabis.

Scarcely believing it myself, I decided to head down and take a whiff for the anniversary of what is known locally as the "Big Smog" approached.

Arriving at Downham Market station after a two-hour train journey from London, myself and the photographer ordered a taxi and made our way toward the British Sugar factory. I had been told in no uncertain terms that the owners have never, and will never, facilitate visits onsite due to commercial and security considerations.

In the cab, our driver told us he had taken people—who had not revealed the purpose of their visit —to the site before. "People don't tell me who they are," he said, as we drove deeper into the countryside. "I just bring them here."

The British Sugar glasshouse

We took a detour down a private road with signs pointing toward the "Riverside Glasshouse" and approached a security gate blocking our path. Then, as if by magic, it lurched open and we proceeded down a dirt track in the shadow of a massive greenhouse.

Our taxi dropped us at the door of the facility, where a security guard met us—accredited journalists—and said he would get his manager. By this point, we could almost smell it ourselves.

Within the plant, British Sugar grows a "key ingredient" for GW Pharmaceuticals, a biotech company which has developed the cannabis-derived Epidiolex, an experimental treatment for severe forms of childhood epilepsy—a condition without an effective treatment.

The yield from this site makes up the majority of the UK's exported cannabis-derived medication. GW Pharmaceuticals' Sativex, an anti-spasticity drug containing a 1:1 ratio of THC to CBD—the principal psychoactive component of cannabis and a nonpsychoactive, highly therapeutic component, respectively—is sent to 30 countries around the world, but is expensive and largely unavailable on the NHS. A considerable amount of purified CBD is exported to the US. In 2016, the UK produced 95 tons of legal herb and exported almost 68 percent of the world's total medicinal weed.

This glasshouse alone provides enough cannabis to treat 40,000 children around the world every year. However, for children in the UK—such as Alfie Dingley and Billy Caldwell, for whom cannabis is a potential savior from their debilitating conditions—the medicine they need remains perilously out of reach.

"The breathtaking hypocrisy of the government allows them to declare in law that cannabis has no medicinal value, whilst simultaneously accounting for nearly half the world's medical and scientific supply," says Paul Flynn, a Labour MP who introduced a bill to legalize medicinal cannabis earlier this year. "The UK's 50-year drugs prohibition catastrophe of increasing drugs use, deaths, plus vast costs, staggers on."

Caroline Lucas, a Green Party MP and chair of the parliamentary group for drug policy reform, echoes his remarks. She says the government's policy on medicinal cannabis fails to follow the evidence and "stinks of hypocrisy."

"It will astonish most people to learn that Britain is one of the largest producers and exporters of medicinal cannabis—yet we have extreme laws that prevent people here from feeling the benefits of these drugs," she says. "As the case of Alfie Dingley showed, the current rules prevent people from getting the treatment they need, despite many health professionals speaking out. The tide is turning across the world on this issue; we now need to catch up."

Campaigners also question how the government can define cannabis as having no recognized medical benefits while exporting more of it than any other nation.

"We demand this blatant hypocrisy is addressed immediately," says Jon Liebling, political director at the United Patients Alliance, which represents the interests of medical cannabis patients in the UK. "It is the only honest and compassionate thing to do."

Liebling points to the absurdity that around 1.1 million UK citizens consume cannabis regularly as a medicine to help manage debilitating and chronic conditions while risking arrest and prosecution. "Citizens from other countries benefit from legal products made from the raw cannabis which we export," he says.

It is understood that British Sugar was granted an exceptionally rare "high-THC" Home Office license in 2016, allowing them to grow the plant on their premises. In a bizarre coincidence, Victoria Atkins, the drugs minister, is married to Paul Kenward, the managing director of British Sugar. Her brother also works for Burson-Marsteller, a PR company which represents British Sugar—from whom she has accepted hospitality.

Recently, she stopped defending the government's cannabis policy after she was accused of a "massive conflict of interest" and "hypocrisy on a grand scale" due to her husband’s business dealings, sparking calls for her to step down.

However, she was not yet in post when the company chose to switch part of their horticultural operation from tomatoes to cannabis. The decision is understood to have divided opinion among the surprised employees in the greenhouse—some were ecstatic, others less than unimpressed.

In Downham Market, where residents were variously perplexed, overwhelmed, and amused by the pungent cannabis smell last year, locals are unconcerned that vast quantities of cannabis are being cultivated nearby. Many support legalization, and our questions often provoked a cheeky wink-wink-nudge-nudge response.

What do you think of cannabis production in the area, I asked one shopper: "There's not enough of it!" she replies.

Others were slightly more sincere in their responses.

"We called it 'the great smog' last year," said Brendan Morgan, landlord at The Swan pub. "It was all over town—it was horrendous, overpowering, and gave me constant headaches. For two days it was worse than the Icelandic ash cloud, but no one knew what the smell was. I've never known anything like it."

Could you not work out what the smell was? "I asked a few of my friends what it was, and they said, 'It's the 'nabis factory over the road,'" said Joanna May, who had to explain to me what 'nabis is. "I just thought, What?! I’ve never heard of anything like it."

The scent does, however, seem to have since subsided.

"You often smell it in the cities and more populated areas, not in Downham," said Chloe Goldsmith, who studies Film at the nearby Anglia Ruskin University. "Coincidentally, though, I got a waft of it just now as I was walking up the street." She summed up the general mood of those we spoke to: "If it is medicinal and it's genuinely going to help people then I don't have a problem with it."

A rundown Conservative Party Association club sits front and center on the high street opposite the Barclays, next to which is a Greggs. These parts are staunchly Tory, seemingly more by habit than conviction, and the MP for South West Norfolk has been a Tory since 1964.

Liz Truss, the current member of parliament for the area, became embroiled in the smell saga last year and accompanied a group of concerned residents on a visit to the factory to help dispel the mystique. However, the cannabis had been harvested and processed by the time the local delegation visited, meaning the smell was barely still lingering.

It was much the same when we visited: From a vantage point on top of a grass verge adjacent to the greenhouse, we discovered what was essentially a bare vineyard. The plant is grown and harvested according to 16-week cycles, and we had apparently just missed our chance of catching the crop in full bloom.

Of course, security wouldn't have let us in to get a closer look anyway; they weren't too happy we had even tried to sneak a peek from outside.

After it eventually emerged that the stench-wave was caused by its first cannabis harvest, British Sugar promised it was looking at measures to "reduce the intensity and impact" on its neighbors in the future.

Meanwhile, the government maintains its spurious position that cannabis has "no medical uses," while the exportation of the 5,000-year old plant continues apace.

Some names were changed.

Sign up for our newsletter to get the best of VICE delivered to your inbox daily.