Fifteen years ago, Sugata Mitra, a scientist from Calcutta, conceived of an interesting experiment. He went to a slum in Delhi, installed a computer into a public wall in the manner of a cash machine, then he waited to see what would happen.

As he had expected, the local children crowded round and began to experiment — but what he had not expected was how very quickly the kids mastered the basics of computing and began to search the internet for new areas of study.