India, Feb. 21 -- Around 15 years ago, when rich Indians began shifting to Dubai, the joke was that the really rich guys went to London and enjoyed the non-Dom tax benefits available to expat millionaires. The not-so-rich fat cats were the ones who went to Dubai because life there was cheaper than in London.

No longer.

One of the more unexpected developments over the last decade has been the slow collapse of London as a desirable city of residence for the world's rich. Partly, it is that the British government, facing domestic pressure, has sharply reduced the tax breaks available to foreigners who want to live in the UK. Even more important than the end of the non-Dom era has been the alarming rise in robberies and knife attacks on the...