The high-pitched squeal of nitrous oxide canisters hisses over reggae.

Incense swirls over green cakes and melon.

Around 30 or 40 people are sitting on Hampstead Heath, chatting about their love of hallucinogenic drugs.

It's the monthly social for the Psychedelic Society, a group of people who campaign for a "better understanding of psychoactive substances".

One person they think needs to do his homework on drugs? David Cameron.

They think the government's plans to ban legal highs won't work.

They are planning to inhale nitrous oxide, or laughing gas, en-masse, in protest outside parliament next month. It's one of the drugs that will be banned under the Psychoactive Substances Bill.

A few members explained to Newsbeat why they thought the new drugs laws were ignorant.

Ryan Dancey, 21, said: "You can't categorise everything under one label.

"You have to look at each high in its own right and look at the particular harm that drug does.

"Spice is definitely bad for you so it should be illegal but other highs might have no physical harm."

Spice is a synthetic cannaboid, a substance produced in a laboratory to mimic cannabis.

It was originally popular because its chemical make-up meant it fell outside the Misuse of Drugs Act, but it was made illegal in 2009.

Recently five students from Lancaster University ended up in hospital after reportedly taking Spice.

The Psychoactive Substances Bill is unlike any other drugs law as it's a blanket ban on all psychoactive drugs.

The government says the new law is urgent and police need greater powers to tackle legal highs.

It says that if it bans substances individually, sellers merely tweak the chemistry to get around the act.

One young man who petitioned the government to close down head shops, which sell legal highs, told Newsbeat earlier this year how legal highs had ruined his friends' lives.

"I've watched them become homeless and look nothing like they used to," he said.

"They're just staggering up the high street, they sleep on the streets now, under bridges."

Despite experiences like this regularly hitting headlines, Paul, a 29-year-old barrister who didn't want to give his surname, said he thought banning legal highs was a bad idea.

Wearing sparkly sequinned leggings and a peacock ruff, he spoke passionately about the issue.

"People at festivals are still going to want to get high, they are still going to want to do something, so what else will they turn to?

"Hopefully it will be to something that doesn't harm them, but who knows? The problem with going down the illegalising route is sometimes it has unintended consequences."

Laughing gas canisters are often seen on festival sites.

Despite the perception that it is a relatively harmless drug, inhaling too much can lead to death.

People who support the ban say that young people don't realise they are dangerous because they are legal.

DrugScience, an independent scientific body on drugs, says the gas is "one of the least risky drugs" but adds that it can kill you.

"Breathing the pure gas directly from a tank using a mask on your face may be fatal because it can cause oxygen deprivation. Filling a bag with the gas from a tank and putting it over your head can kill easily."

In June, 22-year-old Aaron Dunford, a student at Brighton University, died after inhaling laughing gas.

In a debate in the House of Lords earlier in July, Lord Condon, who used to be the Met Police Commissioner, said: "There is real confusion among many vulnerable, naive youngsters, who assume because there are head shops or stands at music festivals selling these substances, they must be medically safe."

It was a different legal high Paul wanted to talk about, one similar to LSD.

"I took this drug and I listened to some beautiful classical music and went to my favourite part of London," he says.

"St Paul's Cathedral looks amazing on acid.

"The geometry and proportions of the building are perfect enough anyway but on acid they are really stunning. I was listening to this beautiful music and looking at this beautiful building and it was probably the closest I ever got to God that night. I'm not religious but it was one of the most spiritual experiences I had."

That wasn't always the case though.

"I had one trip on the illegal kind of acid and it was a bad trip," he says.

Taking LSD and substances like LSD is risky.

Frank, the government's drug education service, says that people have been known to harm themselves during a bad trip.

The site also says that LSD could have serious, longer-term implications for somebody who has a history of mental health problems and can trigger problems that may have gone unnoticed before.

Hallucinations can happen again.

Some people at the picnic said media "hysteria" had caused misconceptions about taking drugs.

Luke Duffy, a 29-year-old baker, said: "It's more about political sway, people wanting to be voted back into power. We need laws based around scientific research rather than public hysteria and ideas some media promote to create fear around the subject."

The government says so far not a single drug has been referred to the independent drugs council without being found to be harmful.

Yet 26-year-old Aaron believes the new drugs legislation is ignorant.

It's his first time at the picnic after having a positive psychedelic experience that "allowed him to see the world in a different light".

"Banning legal highs protects people who don't have the education and don't understand what they are really doing in many cases.

"Banning is probably the wrong approach to have though. The best approach is probably let's research, let's educate, and let's make it so that everybody knows what they are doing before they get in that situation."

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