When I finished journalism school, more than a few years ago, I was given a certificate entitled “Training for Truth”. There has long been a strongly held — but, to many, overblown — belief that the media is the fourth estate. Its purpose is to speak truth to power.

We could endlessly debate how well the media has performed that function. It might take us even longer to agree a satisfactory definition of truth. But for most of the postwar era, the mainstream media in the Anglo-American world has helped shape the political debate by creating a common national narrative.

Now, we are told, the atomisation of traditional media and the spread of social networks has meant we all live in our own “filter bubbles”. Technology has eaten the truth. We live in a post-truth world in which we can ignore the facts we do not like and tap into any personalised narrative that we desire.