SYDNEY - Australia diver Matthew Mitcham announced his surprise retirement on Thursday after winning gold at the Beijing Olympics and 2014 Commonwealth Games. The 27-year-old, who won the 10m platform in the 2008, had been expected to compete in Rio this year. With his final dive in Beijing he claimed the highest individual score in Olympic history. "I have achieved everything I hoped for, including the big three -- Olympic gold in 2008, world number one in 2010, and Commonwealth gold in 2014, which could never have happened without all the help I've had along the way," Mitcham said. "I have no doubt that Grant Nel, James Connor and Domonic Bedggood, along with our girls, will do Australia proud at the Rio Olympic Games this year." He said he would pursue media and entertainment opportunities.