Now we have some data that shows the trend is not just perception. Neal Hudson, an analyst at Savills, a big estate agency, produced the graph below and the map above, which shows the change in the number of people working in media, culture and sport in each London borough between the two censuses of 2001 and 2011. It works well as a rough proxy for "coolness" - albeit one in which your correspondent presumably counts as cool.

FOR young, upper-middle-class Londoners, the game of the moment is guessing where the cool kids will be going next. Gentrification, which progressed gently through neighbourhoods in Islington and Camden in the decades after the second world war, is now changing the city at terrifying pace. The frontier of where you can buy a cocktail in a jam jar is moving like German tanks through the Ardennes: from Shoreditch to Dalston; Brixton to Peckham; Bethnal Green to Hackney Wick.

And the trend is clear. In Camden, where the cool kids of a decade ago moved, the number of people working in the media has fallen since 2001. So too in Kensington and Chelsea and Hammersmith and Fulham: West London redoubts such as Notting Hill are all occupied by bankers now. Instead the 22-year-old journalists, playwrights and artisan bakers are moving eastwards. Tower Hamlets and Hackney are where they are ending up.

The best explanation for this is house prices and rents. Young creative types aren't paid all that well. Young management consultants, bankers and lawyers, by contrast, are. And as they've followed the artists and advertising copywriters into trendy neighbourhoods, they've pushed up rents and house prices so that the creative people can't move there anymore. As Alex Proud, a nightclub owner, laments in an amusing piece in The Telegraph, "you can play a nostalgic little game where you remind yourself what groups London’s inner neighbourhoods were known for 20 years ago. Hampstead: intellectuals; Islington: media trendies; Camden: bohemians, goths and punks; Fulham: thick poshos who couldn’t afford Chelsea; Notting Hill: cool kids; Chelsea: rich people. Now, every single one of these is just rich people."

Is this a problem? It is tempting to think so. There is nothing gentrifiers dislike more than other gentrifiers, especially much richer ones. But on the other hand, the shift reflects genuine social progress. Trendiness alone has not driven change. Twenty years ago, few middle-class people wanted to live in places like Hackney, because crime rates were high, congestion legion, pollution choking and the schools utterly appalling. All of those things have improved enormously. And an influx of middle-class people has probably helped entrench the changes. Not all existing residents benefit because some have to rent in the private sector, and rents are up. But most are shielded: either because they own, or because they live in subsidised social housing.

In any case, gentrification is here to last. The trends that are making city centres more pleasant to live in seem set to continue. Politicians do not want to allow much building on the green belt, which helps to explain why people are not moving to the suburbs in the droves that they once did. And if London's economy stutters such that it stops producing so many well-paid bankers and lawyers, artists and writers will not do much better. Better get used to the change then.