As the FT notes this morning:
It is fashionable these days to portray London as a nascent city-state, a world city pulling away in wealth and status from the rest of its benighted country – “a first-rate city with a second-rate country attached”, as one American working in London’s financial district put it.
Now I should add that the article half-heartedly concludes that such a separate City state is for now impossible in the current UK political climate. However, the article still seems to me to be an exercise in kite flying for an idea that it its author, Brian Groom, clearly has sympathy for and for which he perceives there to be a groundswell of support, at least within the City's limits.
As he puts it:
A low-tax London could set policies as international trading hub, while whatever was left after London and possibly Scotland had been carved out could, for example, aim to encourage manufacturing while ridding itself of England’s centralised government system.
Yes, that's fantasy for now, but someone clearly has that fantasy. And the reality is that those who have that fantasy do want tax haven London to break away from the rest of the UK.
Don't rule out the suggestion gaining momentum as the 'recovery' begins and those in the City see themselves being weighed down by the need to redistribute what they see as their wealth to the regions of the UK. Then the clamour for London to keep what it sees as its own wealth may create a real divide in England, let alone the UK.