But even if you can give that up and you have enough supply to import all your food from elsewhere in the world, how are those imports going to get into London? There's limited spare capacity for freight ports on the Thames. Even if you could finish the London Gateway -- which isn't actually in London anyway, and you probably couldn't build anything like it further in -- and significantly expand its capacity from what is currently planned, you'd still need the warehousing and logistics to go with it, and then you'd need all the staff to build and maintain and operate all of this, and then the supporting infrastructure and services to go with those staff. That's an awful lot of new space and new relatively low-paid workers to fit into your hypothetical newly-independent London, just to make up for not having land-based supply of food and drink.

So again, as I have said repeatedly, London is only disproportionately strong economically because it is primarily based on high-margin service industries and relies on the rest of the UK to supply much of the low-margin infrastructure it needs for the basic operation of a city that size. You can argue over whether that beneficial financial arrangement is literally rent-seeking, but certainly the economic effect is similar: London currently benefits disproportionately from the UK's public spending and government-supported infrastructure, but that spending and infrastructure development is only possible because of what is also going on elsewhere in the UK.