The sign language interpreter at the Nelson Mandela memorial event says he had a schizophrenic episode on stage.
Thamsanqa Jantjie insisted he was fully qualified, but began to hear voices as he attempted to interpret the speeches, causing him to lose concentration in the eyes of the world.
There was an outcry after the ceremony on Tuesday when it was revealed that his gestures had made little sense.
He had repeatedly mimed the words 'prawn' and 'rocking horse', deaf people revealed.
"There was nothing I could do. I was alone in a very dangerous situation. I tried to control myself and not show the world what was going on. I am very sorry, it’s the situation I found myself in,” he said.
The 34-year-old said he could not leave the stage, so carried on signing things that did not make sense.
“Life is unfair. This illness is unfair. Anyone who doesn’t understand this illness will think that I’m just making this up,” he added.
He also told South Africa's 702 radio station that he was "absolutely" happy with his performance.
"I think that I've been a champion of sign language", he added.
More information about schizophrenia here.