Gentrification is so last century: the world’s elite cities are going a step further.

Today, the most desirable big cities – New York, London, Paris, Hong Kong and so on – are undergoing “plutocratisation”, writes Simon Kuper in the Financial Times.

Fresh from attending the New Cities Summit in São Paulo, Kuper advises that “our great, global cities are turning into vast gated citadels where the elite reproduces itself … The middle classes and small companies are falling victim to class-cleansing. Global cities are becoming patrician ghettos”.

He writes:

The great global cities – notably New York, London, Singapore, Hong Kong and Paris – are unprecedentedly desirable. At last week’s fascinating New Cities Summit in São Paulo, the architect Daniel Libeskind said: “We live in a time of renaissance … cities are coming back to life, after a long neglect.” Edward Luce chronicled the urban revival in last Saturday’s FT Magazine. However, there’s an iron law of 21st-century life: when something is desirable, the “one per cent” grabs it. The great cities are becoming elite citadels. This is terrifying for everyone else.

While the service workers commute from the suburban fringes, the populations of these elite cities enjoy the privileges of a one-percenter urban paradise, he says, drawing on a conversation with Saskia Sassen, a writer on cities from Columbia University.

Elite members don’t live there for their jobs. They work virtually anyway. Rather, global cities are where they network with each other, and put their kids through their country’s best schools. The elite talks about its cities in ostensibly innocent language, says Sassen: “a good education for my child,” “my neighbourhood and its shops”. But the truth is exclusion.

When one-per-centers travel, they meet peers from other global cities. A triangular elite circuit now links London, Paris and Brussels, notes Michael Keith, anthropology professor at Oxford. Elite New Yorkers visit London, not Buffalo.

In Britain’s case, London is widely seen as a different place – a different country, even – from the rest of the nation.

“A first-rate city with a second-rate country attached,” is how an American friend of Stephanie Flanders put it.

The quote neatly sums up the way the plutocratised citizens presumably see their homes – and is used by the BBC economics editor to introduce her summary of a film that appeared in March addressing the gap between the capital and the rest of the country.

In the Guardian, meanwhile, recent pronouncements by Mayor Boris Johnson on London’s future have inspired the reliably brilliant Aditya Chakrabortty to write from the future – 2030, to be precise – reflecting on London’s secession from the United Kingdom.

What began as a call for Holyrood-style devolution got louder and more ambitious, until in 2029 Londoners found themselves voting in a referendum on whether to go independent. Boris himself had long left the political stage, contenting himself as a non-exec for the world’s biggest, Shanghai-based, bank. But from the bikes, to the buses to the museums; Londoners knew they were Boris’s people.

There were anxieties of course. What currency would the new city-state have? Borisstan would eventually enter a currency union with the Chinese renminbi. Where would the energy supplies come from? How would Londoners get rid of their landfill? As soon became apparent: “London” had always meant two different things. There was the small central area, where new properties were sold off-plan to foreign tycoons and where Londoners were nothing more than glorified butlers to the global plutocracy. This was the city as a docking station for international capital.