Security allow 'legal high' laughing gas at festival
27 August 2014 Last updated at 20:38 BST
Widespread consumption of laughing gas at one of the UK's top dance festivals has been exposed by a BBC investigation - as security stood by and did nothing.
The Home Office recently urged festivals to crack down on laughing gas. But reporters posing as partygoers found the drug being taken openly at South West Four on Clapham Common.
Some security guards watched the drug use - one calling it "not my problem". Organisers say they treat legal highs on a par with illegal drugs.
BBC London's Tarah Welsh spoke to Dr Owen Bowden-Jones, from the Central and North West London Club Drug Clinic, and Norman Baker, the minister of state for crime prevention.