He became the first ever double amputee to compete in the Olympic games. His picture was plastered across billboards worldwide as a symbol of triumph over adversity, and he became one of the world's most recognisable superstars. Oscar Pistorius was the face of London 2012. Yet just six months later, he was arrested and charged with the premeditated murder of his girlfriend Reeva Steenkamp. How could such an admired sporting champion and role model to millions be involved in such a shocking event?