A decade ago, Biz Stone, a tech entrepreneur, was drinking in a bar in Austin, Texas, when he had an exciting vision. His company was launching an online platform that could dispatch short messages — a technology first developed to transmit vital information for, say, emergency services.

But as Stone looked at the drinkers huddled around the bar, he realised that short digital messages might enable people to huddle too, around a common idea, cause, joke or plan. “I had the image of people flocking together, like birds,” Stone told me a few years ago, explaining how his company created Twitter. He presumed that such technologies would connect humans — and create a more harmonious world.

How times change. This month that optimistic idea has been visibly rebuffed: tweets from Donald Trump, along with those of his opponents, have caused people to fly apart, not flock together.