For America’s wealthiest citizen, austerity is relative. The retinue of staff and the private jet hint at a fortune said to be approaching £40 billion. As he told pupils at a south London school he visited this week: “If I hadn’t given my money away, I’d have had more than anyone else on the planet. Ninety-nine per cent of it will go.”

In an era when the wealthiest are society’s pariahs, the Microsoft founder has become the people’s plutocrat. Although some diseases, such as malaria, remain rife, his charitable foundation and his lobbying have borne results. In the past year, not a single citizen in India contracted polio.

“People think aid is abstract and thousands of miles away. I go there and see it. I’m intent on making sure that my money gets to people who need it, and I come back and say it’s working.” This message has been heeded by “Cameron and George,” who have promised to hit the recognised goal of spending 0.7 per cent of GDP on aid.

Is he not disappointed that Mr Osborne will effectively be cutting the budget by more than £1.1 billion over three years, because the economy is shrinking? “I have nothing but praise for the UK. [The drop] is certainly unfortunate, but I can hardly complain about it. 0.7 per cent is the gold standard, and most countries aren’t living up to that.”

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