The other day, a senior figure in the US government showed me some pieces of old paper he has taken to keeping in his pocket. These scraps, he solemnly explained, were used for jotting down words or numbers which he needed to remember or communicate to other officials – such as sensitive data about banks or the budget.

Now, you might wonder why he needs such scraps, given that we are supposed to live in a brave new digital age. After all, paper is a fragile and inefficient way to keep notes or communicate to a wide pool of people, compared with a blackberry, say.