Which legal and financial instruments have defended the City of London itself from being auctioned for parts?

Subsets of culture are preserved, packetized & traded daily. Even StubHub has a "food festival" category.

Before learning that this[1] was a thing, I honestly would have interpreted your remark in passing as figurative rhetoric.

[1] https://en.wikipedia.org/wiki/London_Bridge_(Lake_Havasu_Cit...