More than 200 years ago it was already possible to send messages throughout Europe and America at the speed of an aeroplane – wireless and without need for electricity. Email leaves all other communication systems far behind in terms of speed. But the principle of the technology – forwarding coded messages over long distances – is nothing new. It has its origins in the use of plumes of smoke, fire signals and drums, thousands of years before the start of our era. Coded long distance communication also formed the basis of a remarkable but largely forgotten communications network that prepared the arrival of the internet: the optical telegraph. Every tower had a telegrapher, looking through the telescope at the previous...