FOR Bill Gates, the wealthiest man in America, who turned up at the Deptford Green School in South London after it had asked for “someone with an interest in global issues”. Mr Gates spoke for two hours about his career at Microsoft and then asked the children what he should do with his money to make the world better place. He knows, of course. One of his aid projects has eliminated polio in India and he has just announced a $750 million pledge for tackling Aids, malaria and TB.