The City of London is an unusual corporation inside what is usually described as London. So unusual that it has its own interesting member of Parliament, a "remembrancer" whose job it is to remind Parliament of the privileges of the City, and take exception to laws which might alter or harm it.
It looks like the EU, however, has decided to take over regulation of the City of London's financial firms: and there is no remembrancer to stop politicians who don't know what they are talking about from imposing whatever regulations they see fit. While there was celebration of the regulations by Congress that moved business to the City by City financial firms, it looks like they might have their own problems in the future. And may move to less constrained places, like Singapore.
Which would be a pity.