Most books about the internet are written by excitable youngsters who inhabit the bodies of middle-aged men. This one is different, for the authors have identified one of the very rare moments when a fundamental shift in government, business and even our view of causality is taking place.

The reason ‘Big Data’ is so important is that, unlike email or even Facebook, it’s not just a mechanism that lets us do, albeit more efficiently, what we were always going to do – send messages, say, or link with friends. Instead, it’s more like the invention of the microscope, or financial accounting, or time-lapse photography: it’s a new tool that allows us to see activities hitherto invisible to human awareness.

Here is an example of the old approach compared to the new. In 2009 the dangerous flu virus H1N1 was spreading around the world. In America, the Centers for Disease Control and Prevention (CDC) in Atlanta shifted to high gear. All doctors were instructed