The hunt is on for the fake sign language interpreter who took to the stage during the memorial for former president Nelson Mandela yesterday, gesticulating gibberish before a global audience of millions and outraging deaf people across the world. While dignitaries were addressing the crowd in the 95 000-seat FNB stadium, the young, suited man stood within metres of US President Barack Obama. He had an official security pass round his neck, but no-one seems to know who he is, raising serious security questions. "He was basically gesturing. He didn't follow any of the grammatical rules and structure of the language. He just invented his signs as he went along," said Delphin Hlungwane, an official South African sign language interpreter at DeafSA.