If you want an accurate picture of the rich bits of London today, look at the poverty maps drawn up by the social reformer Charles Booth in 1899 as part of his Inquiry into Life and Labour in London. Using a colour-coding scheme, Booth shaded different parts of London according to wealth.
He painted the lowest class - "vicious and semi-criminal" - in black. The very poor - "casual or chronic want" - were in dark blue. And the "upper-middle and upper classes - wealthy" were in yellow.
With uncanny symmetry, the same colour scheme would apply to modern London. The city still looks some great big bruise, gradually healing the further west you go: black and blue in the East End; red or middle-class in the fashionable old bohemian villages of Camden and Islington.
And the bruise turns yellow in Belgravia, along the fringes of Regent's Park and south-eastern Notting Hill.
The big difference now is the nationality of the people making up the yellow bits. In 1899, those richer classes would have been almost entirely British, with the odd European noble emigré among them.
There are quite a few rich British people still there. The big change is that they have been joined by a mass influx of international rich - the biggest in London's 2,000-year history.
Now you have a new phenomenon: the international rich choosing to leave their native countries, and all heading for our yellow bits.
The other thing that has changed is the extent of the wealth: the fortunes held by hedge fund managers and Russian minerals and utilities oligarchs are so great that Booth would have to invent a new, richer shade of yellow to describe them.
A lot of the new billionaires are leaving perfectly functioning countries to come here. The American voices you hear in Mayfair are more likely to belong to residents than tourists these days.
Some of the regimes the new billionaires are leaving are still inhospitable, though. It's striking that most of the great billionaire Russian oligarchs are Jewish: Boris Berezovsky and Chelsea owner Roman Abramovich are only too aware that President Putin has appealed to voters through tacit anti-Semitism.
London has become Gotham, with great tides of wealth sluicing through the streets, and international men of crime riding the crest of the wave behind.
A decade or two ago, the Russian dissident Alexander Litvinenko wouldn't have been murdered in London and there would have been no attempt on Boris Berezovsky's life. That's just for the simple reason that the billionaires and the dissidents wouldn't then be seen dead - or alive - in London. New York, Paris or Monaco would have been their natural destination of choice.
How gripping, by the way, that Litvinenko had his sushi garnished with polonium-210 in Itsu, a smart Japanese restaurant in Piccadilly, and Berezovsky's would-be assassin was arrested at the Hilton on Park Lane.
If Charles Booth were around today, he'd have to elide the yellow and the black areas into a bee-striped category where international riches meet international skulduggery - "upper-middle and upper classes, wealthy, vicious and semi-criminal".