[dragonwriter]

> With a hard Brexit, that all disappears because the only reason London is the economic powerhouse that it is is because of its position within the EU.

This may be the only reason it has retained the role, but it had the role for a couple centuries before the EU, largely due to its historical position in the Empire and inertia. I don't think the essential connection of the role to the EU is universally accepted. Though we'll certainly see if it's true...

[Arizhel]

The Empire is long since dead and gone, and small has-been nations with little significant industry cannot retain world-leading status forever on inertia alone. Just look at Italy; where are they now? They make some great olive oil I guess, and a few really nice cars, but they're not the powerhouse they were 2000 years ago.

The essential connection of the role to the EU may not be universally accepted, but it's also not universally accepted that the world is round or that humans visited the Moon. The EU countries are more prosperous economically for the same reason the US has been prosperous for a long time: having tons of different currencies and massive transaction overhead (customs, duties, different regulations to follow, etc.) every time you cross a border is bad for economies. North Korea is a good example of how a country does economically without significant trade.