To visit Silicon Valley these days is to take a rocket ride into the future. The breathless talk is of another surge in technological innovation, the rapid development of virtual reality, driverless cars, 3D printing, robots, personalised medicines, the application of artificial intelligence to masses of data and of further disruption in almost every nook of the economy.

It is an exhilarating, disorienting and at times downright scary experience.

Turning on the television while visiting Silicon Valley, in a bid to catch up with the presidential election campaign, is to crash back to Earth with a thud. The talk is of income inequality, the collapse of the middle class, the banning of Muslim visitors and the building of walls to stop immigrants pouring into the US.