Demonstrators have protested against Government drug policy by staging a mass inhalation of so-called "hippy crack" or laughing gas in the shadow of Parliament.
Hundreds of people were expected to turn out to inhale the gas in Parliament Square to protest plans to make it illegal - but the number turned out to be just dozens.
People attending the event pointed out that there seemed to be more journalists and photographers present than actual drug-takers present, as the protest stunt seemed to fall a little flat.
— Simon Conway (@SimonConway) August 1, 2015
Nevertheless, the few who were there filled balloons with nitrous oxide and simultaneously breathed in, erupting into giggles and laughter before spreading out across the lawn.
The Government announced plans in May to introduce a law to ban any mood-altering drugs or "legal highs" that are not specifically exempt under current legislation, meaning the popular laughing gas would no longer be permitted by law.
Stephen Reid, founder of the Psychedelic Society, wrote in a blog for The Huffington Post UK: that "the Government's rationale for prohibiting trade in psychoactive substances is that their use can be risky.
"Yes, the use of psychoactive substances can be risky, but it should be for individuals to decide whether or not to take the risk.
"People should be able to buy, sell and use whatever substances they want, so long as there's no harm to others."