A few minutes' walk from Tufnell Park station in north London, a steady stream of teenagers is flocking towards an industrial area. Muffled 140bpm beats thud through the walls of a warehouse, where a crowd gathers outside a door that’s clearly been forced open. The crowd is young, and the music is mostly drum’n’bass. Inside the warehouse, the first thing we see is a ‘Nos’ bar, selling nitrous oxid