Arguably it is London:
…nearly one-third of the FT100 top companies has a non-national as chairman or chief executive. No other country has anything like that proportion.
Britain now publishes more book titles than any other country. Further example: there are more Chinese students in the UK than in any other country, again more than the US.
I can remember when the problem was keeping the Brits in, not keeping the foreigners out. But the UK had the good sense to embrace globalization rather than fighting it. Is there a lesson in this for you-know-who?