There's something rather brilliant about bringing together members from three of punk's most inventive and uncompromising bands for a 50th anniversary celebration. X-Ray Spex, The Raincoats and The Slits were never about playing it safe, they challenged what punk could be, so a supergroup reunion feels like the right kind of chaotic energy to mark half a century of the scene. If you've ever wondered what happens when that much creative defiance shares a stage, this London festival might be your answer, and the previously unseen artwork and photography should give us fresh insight into those wild early days too.