By Si Hawkins

Really, you’ve never seen a mosh pit like it. Wave upon wave of frenzied shorties cascading toward the stage, minds super-stimulated by the raucous rhythmic din and inhibitions long-since abandoned as they shriek themselves hoarse; not that they had many inhibitions to begin with.

Dotted perilously along the imaginary line that once separated this manic throng from its target are a couple of hapless security guys, struggling manfully but hopelessly to keep some kind of order. The look in their eyes is pure, unprecedented panic. They’re slowly being submerged under a sea of kids.

We’re at something called the Underage Club, a popular all-ages bash run by the 15-year-old son of an eminent experimental musician, held in a converted Victorian cinema in South London, and headlined this afternoon by the country’s oddest new must-see band, The Horrors, who are causing …