am a late adopter of new technology, so I only recently discovered that an age-old urban problem had been solved. I was in a restaurant with friends. Outside it was cold, and on Sundays the bus ran only every 20 minutes. When to go to the bus stop? My friend pulled out his smartphone, and told me when my bus would arrive. It was a little trick - like finding another friend's house on my smartphone's GPS with three tired children in tow - but it made urban living easier. Thanks largely to smartphones, this is probably the best time ever to live in a packed city.

As my economics guru Stefan Szymanski explains, when the internet arrived many pundits predicted the decline of cities. After all, why live in a flat in Hackney when you could send emails from an old farmhouse overlooking a sheep meadow? But the prediction was wrong. Overcrowded, overpriced cities only became more popular, which is why Hackney flats have got so expensive. Meanwhile the countryside has turned into something of a desert, inhabited by farmers and old people, and used by the rest of us chiefly for long walks. In 2008, for the first time ever, most humans lived in cities.

They are lured by social networks. To be rural is to be isolated. You live in a village or suburb to have space, not to meet people. But cities create contacts. Someone you run into at a party or your kids' playground can give you a job or an idea. The perfect one-on-one urban encounter combines mating, education and business development over a cup of good coffee. Mathieu Lefevre, executive director of the New Cities Foundation, says: “In a dense city you have these two-minute chance encounters that make your life richer. You and I have nothing in common, but maybe we meet and start Facebook together.”