The last opera in Stockhausen's Licht cycle to remain unperformed, Mittwoch received its belated world premiere on Wednesday. It would have been the composer's 84th birthday. Had he still been around, he would have performed the part he wrote for himself - compere of the notorious Helikopter-Streichquartett. That role was assigned instead to the cheesily effective ("Let's hear it for Stockhausen!") DJ Nihal, who rattled the chin-stroking fraternity by treating the whole thing as a Radio 1 Big Weekend with beards.