What should the comfortably off of the world do to help the poor? We could build dams, railways and roads. We could fund education or public health. We could lower our tariffs and let them sell things to us. We could advise them on appropriate economic policies. (I know, I know.) Or we could leave them alone, on the grounds that our help may be doing more harm than good.

But here's an alternative: why don't we just give them money? For such a forehead-slappingly obvious plan, it's received relatively little attention until the past few years. Until recently it has been hard to reach the very poor directly. Making sure that welfare payments go to all and only the right people is hard enough in the UK - it stands to reason that it will be a lot more difficult in Afghanistan.

So far we've settled for giving the money to the governments of poor countries instead, often with strings attached aimed at making sure the money is spent on good works. But those strings can be snipped. You may think you're paying for a hospital but if the health minister simply uses your aid money to build a hospital he would have built anyway, and steals the money from his own budget, you're really just paying for his luxury apartment in Monaco.