There was a man on Radio 4 this morning telling us about how many unexpected bird species are living happily in London (this man is a birdist, or something, as distinct from a Twitcher: Twitchers are competitive types, rather like feathered-train spotters; birdists actually know a lot about the birds).

How shall we see these wonderful things? asked the other guests on the programme. When you leave the building, just look up, said our man.

I foresee some bruising encounters. Would-be birdists, heads up, crash head-on into i-Phoners, heads down, texting as they go.