HARRY Potter star Emma Watson has beaten Keira Knightley and Kate Moss in a poll of female icons.The 17-year-old, who plays Hermione Granger, was voted Britain’s greatest female ambassador.Keira was second, followed by Lily Allen, Charlotte Church, Jordan and Coleen McLoughlin. Victoria Beckham only managed eighth placeKate Moss and Girls Aloud’s Sarah Harding were bottom in Top of the Popsmagazine’s poll.Editor Peter Hart said: “A good ambassador needs brains and beauty, not just bags of cash.”