When does a drug actually become illegal? As Glastonbury opens its gates for another year, some festival goers will choose "legal highs" as an alternative to illicit drugs - helped by dealers who are using obscure loopholes to sidestep the law.
Bath salts, fertiliser and cleaning fluid. They hardly sound like streetwise slang terms for recreational drugs. But using descriptions such as these is one way that dealers in legal highs are keeping beyond the grasp of the law's long arm.
On Wednesday, bereaved mother Maryon Stewart is due to meet Home Secretary Alan Johnson as part of a campaign to ban the legal "party drug" GBL. In April, Ms Stewart's daughter, Hester, a medical student, died after taking the drug.
GBL is but one name in a thriving market of legal and herbal highs. As the summer festival circuit moves into full swing, vast quantities of these drugs will be bought and consumed. But you don't need to be in a field to buy them - High Street "head shops" openly sell tablets laced with various chemicals and compounds for about £6 each.
Click online and there's an even more bewildering array of substances on offer.
'I WAS VIOLENTLY SICK'
Electrician Leon Rygol, 24, took herbal pills bought in a tube of six at a music festival in Bristol in 2005
'I was violently ill as the night ended, it was terrifying as I was vomiting every 30 minutes for six to eight hours.
'My friend took the same pills and had to take two weeks off work suffering from extreme paranoia.
'It's crazy they are legal and sold to the general public. I bought them in a place where there were families and kids.'
Legal highs are not new, but stronger variants are evolving, loopholes are being exploited and the mood among health experts and advisers is darkening.
The Home Office is already consulting on plans to outlaw two party drugs - BZP and GBL - after they were linked to the deaths of two youngsters.
BZP, also known as herbal ecstasy, Red Eye, Frenzy and Pep Love, and the industrial solvent GBL are likely to be made illegal next year along with some anabolic steroids.
The Medicines and Healthcare products Regulatory Agency (MHRA) has already banned the sale of BZP, although it's not an offence to possess it.
But, as toxicologist Dr John Ramsey explains, the authorities are locked in a cat-and-mouse game with dealers of these substances. The problem, says Dr Ramsey, who analyses drug "amnesty bins", "is it takes a long while to control each of these compounds and as soon as you control one, another set appears".
"The government is always playing catch-up, there's a lot of money to be made."
Many legal highs are not very different from the current illegal drugs like amphetamines and cocaine, and have similar side effects. These can include heart problems, raised blood pressure, vomiting, anxiety attacks, mood swings, high temperatures and seizures, experts say.
Dr Ramsey says: "People are selling stuff on websites and in head shops to young people who haven't got the remotest idea what's in them. We need to get across to the young consumers and retailers that there are serious unknown risks in what they're doing."
Festival goers are using alternatives to traditional party drugs like ecstasy
Professor Les Iversen, who sits on the Advisory Council on the Misuse of Drugs, agrees. He says legal highs are emerging at an increasing rate, with most not matching up to their claims.
One called Spice, which users smoke, is of particular concern, he says.
Spice contains a chemical linked to the active ingredient in cannabis - and could be up to 10 times stronger, some researchers believe.
Although Spice and other drugs like Salvia, amyl nitrate and isobutyl nitrate do not fall under the Misuse of Drugs Act, that has not stopped authorities seeking to ban their sale.
The MHRA says because they have a physiological and potentially harmful effect on the body, they can be considered a medicine.
That means under the Medicines Act it would be a criminal offence to supply them without a prescription or through a pharmacist.
BZP was first trialled as a worming treatment for cattle, but never widely used as it caused fits in some animals
Khat comes from the leaves and shoots of a plant containing natural speed-like compounds. It's chewed over several hours and is popular in east Africa.
GBL is an industrial cleaner used to strip paint and remove graffiti taken in liquid form
Spice is a powerful herbal smoking mixture imported from China that gives a "cannabis-like" effect
Salvia is a plant related to common sage which gives a short, LSD-style hit when smoked or chewed
It's one of the latest tactics the authorities are employing to clamp down. Earlier this month 20 shops in London were raided by police, Trading Standards and MHRA officers for exactly that reason.
But what do the people taking the drugs think? Paulo, a 40-year-old from south London, says he used to take GBL in nightclubs for its euphoric and energetic high.
Doses are measured with a pipette then added to drinks, because taken neat it would burn your mouth, he says.
GBL is often taken as a substitute for the party drug GHB, which is already illegal.
"It makes you want to dance and your body has a pleasant tingly feeling all over. It's more intense than ecstasy, I think, and doesn't seem to have the horrible comedown in the days afterwards," Paulo says.
'It can be fatal'
"I stopped taking it because I'd seen so many people overdosing. If you take slightly too much, or take your second dose too soon, you can lose consciousness or have a fit.
"It can be fatal so it makes no sense that it's freely available and legal, while relatively harmless drugs like ecstasy and cannabis can carry a prison sentence."
A litre lasting months or years can be bought on the internet for about £100, where it is marketed as a cleaning fluid.
Drug regulators are using the Medicines Act to take sellers to court
This last point is telling. Some retailers and websites are exploiting a loophole in the law by selling their drugs as cleaning fluid or soil fertiliser - however others will be selling these for their stated purpose.
Spice is often sold as "herbal incense" not for human consumption.
Dr Ramsey says: "If you buy something from a high street shop as a tablet or capsule, it's fairly obvious it's to be taken as a drug. It's more difficult selling white powders in plastic bags as bath salts. "The compounds are not illegal and it's not illegal to sell bath salts, it's a very grey area. I doubt anyone who buys these are in any doubt what they're for, it's interesting to know how they know."
The sale of legal highs over the internet makes their control particularly difficult, and the battle between the authorities, manufacturers and retailers has never been more acute.
It's unlikely the festival goers heading to Glastonbury will have the same worries.
Add your comments on this story, using the form below.
I bought some Spice from a shop in town and it was really bad, like inhaling from a hoover bag. The difficulty, as you mentioned, occurs when one substance is banned and another more dangerous substance takes its place. I remember a few years ago when selling magic mushrooms was made illegal (a drug that was relatively safe and non-addictive). Many people simply switched to using Ketamine, which is addictive and far less sociable.
This is similar to the problems America faced during prohibition, with badly home made alcohol causing deaths. Many of the popular recreational drugs would be safe if well made and sensibly taken. By outlawing them there is no quality control and no sensible discussion on usage. Prohibiting something that a lot of people are determined to do is never going to work.
Ian C, London
I have taken a number of drugs for research purposes over the last five years and without any shadow of a doubt Salvia is the most terrifying experience I have ever had. The drug can be smoked in small quantities to give a light, funny high similar to cannabis, however, when smoked in extract form it knocks the user unconscious for 10 minutes which actually seems like several life times in another dimension/reality. Salvia divinorum extract smoked in large doses is in a different league to any psychedelic experience I have ever had, it may only last a few minutes but can seem like (literally) an eternity. Although I don't think any drug should be 'illegal', this should definitely be used with caution and its 'legal' status may give some people a very nasty surprise if they jump into the deep end.
Quit the pathetic attempts to ban drugs and concentrate efforts on quality unbiased education so that potential users know precisely what the effects and risks are of the substance they are contemplating taking. Maryon Stewart is quoted as saying that her daughter would not have taken GBL had she known the risks - that might be wishful thinking, but it is clear that a substance being illegal doesn't stop people using it, but having honest unbiased facts might at least empower informed choices.
Megan, Cheshire UK
Yet more reason to legalise and control the sale of these "social" drugs. If you ensure that only those that are made safely and sold in safer doses then people will get less damaged by the impurities and dangerous experimentation that goes on. Illegal dealers will have less income and the tax revenue would help find the treatment for those who need it. There is very little difference between most illegal drugs and their legal counterparts in alcohol and tobacco but because of shrill cries of "think of the children" the real issues get pushed aside. A rational approach would be nice.
Peter Galbavy, London, UK
Every valid study I've read seems to indicate that we might be better off legalising illegal drugs, rather than criminalising more of them. If we were really serious about outlawing the most dangerous legal drug, alcohol would be the first on the list. I understand Ms Stewart's pain - my own brother died of a heroin overdose - but further prohibitions are not going to magically solve the problem.
Tom Melly, London, UK
Maybe the UK government should do like the US government with its Controlled Substance Analogues act, which banned anything similar to something illegal.
Bruce Mardle, Isle of Wight, UK
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