I will add a mainstream article about the City, so anyone might find the info acceptable

"the Corporation exists outside many of the laws and democratic controls which govern the rest of the United Kingdom. The City of London is the only part of Britain over which parliament has no authority. In one respect at least the Corporation acts as the superior body: it imposes on the House of Commons a figure called the remembrancer: an official lobbyist who sits behind the Speaker's chair and ensures that, whatever our elected representatives might think, the City's rights and privileges are protected. The mayor of London's mandate stops at the boundaries of the Square Mile. There are, as if in a novel by China Miéville, two cities, one of which must unsee the other.

Several governments have tried to democratise the City of London but all, threatened by its financial might, have failed

2011 https://www.theguardian.com/commentisfree/2011/oct/31/corporation-london-city-medieval