Dozens of people have inhaled balloons full of nitrous oxide outside parliament in protest against proposed new drug laws.
The government's psychoactive substances bill would ban the use of substances like nitrous oxide, more commonly known as laughing gas. The bill has been criticised by the government's own advisers, who say the bill goes too far and would have "serious unintended consequences".
A protest against the psychoactive substances bill was organised by a group called Psychedelic Society, who invited dozens of people to inhale laughing gas outside of parliament.
In Parliament Square, in the shadow of a statue of Nelson Mandela, colourful balloons were filled and passed around the crowd.
Around 50 protesters inhaled the gas.
After around 10 seconds of quiet hissing, Parliament Square filled with laughter and scenes like this.
BuzzFeed News interviewed Will Robinson immediately after he inhaled his balloon, although he had calmed down by the time this photo was taken.
"I'm feeling good, yeah, it only lasts for 20 or 30 seconds really, then you're back to normal," said Robinson, pausing to giggle after every few words. "We can't tell what effect we'll have, but there's been a lot of press coverage so we're hoping there will be a fallout from it."
Fellow protester Richard Underwood said he's "not a very big fan" of laughing gas, although he felt the protest was effective. "Having the balloon was fun but it's a once-in-a-while thing – I don't rate it as a very amazing experience. The effects are fairly mild and it's very safe. I'd recommend you give it a try."
Protest organiser and chair of the Psychedelic Society Stephen Reid said he hoped the protest would start a fightback against the bill.
"It's mission accomplished," said Reid. "We're not expecting Theresa May to turn around tomorrow and say she got it all wrong and scrap the bill, but this is just the start of a long process to open people's eyes and show there's a much better way of doing things."
The Psychedelic Society have regular picnics and have monthly meetings in a north London warehouse. Saturday's protest was the group's first political action, but Reid said there will be more to come.
"Psychedelics are an amazing thing," he said. "They consistently result in experiences which people say are the most profound experience of their lives and people aren't aware of it or actively avoid it because of the legal status of these things."
Despite being the protest organiser, Reid said he doesn't like nitrous oxide all that much.
"I'm not a huge fan of nitrous, I use it from time to time," said Reid. "The effect is like going into a trance and then, when you come out of that state, you get the giggles, which is where it gets its name from, obviously."
It remains to be seen what effect the protest will have on the psychoactive substances bill, but it seemed like an enjoyable afternoon for the protesters regardless.
Jamie Ross is a Scotland reporter for BuzzFeed News and is based in Edinburgh.
Contact Jamie Ross at firstname.lastname@example.org.
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