I believe it is more the case that the banking sector in the City of London is the institution, and the secrecy jurisdictions are tools that it developed and uses. Historically money ended up in England because of the Eurodollar system, and from there banks use the secrecy jurisdictions to create trust systems across different jurisdictions for opaqueness. England as an intermediary is preferred because there is a level of trust there with their institutions that isn't there with some bank in a random backwater.

> the banking sector in the City of London

There’s no difference in regulations in or outside the city

> their institutions that isn’t there with some bank in a random backwater

It’s the exact same banks. Here’s a list for Jersey although the same is true for most Crown-controlled tax havens: https://en.m.wikipedia.org/wiki/List_of_banks_in_Jersey

By random backwater I meant some random place that wasn't involved with the major colonial powers during that period. The reason most of the offshore tax havens are what they are is because they were remnants of colonial empire that could be exploited.

I think the path dependency is what made the City of London the hub, and their trust system is how non citizens were able to access their financial system and those in their territories as well. I'm sure now there are ways to access services in these places directly now, but historically, the majority of the infrastructure dedicated to this stuff in these places was built out from England.