London is pretty much the main hub of global finance. All sorts of shady business that you can't even get away with in New York is routed through London. It's the capital for financial fraud and rehypthecation. From there money can be routed through countries like Ireland, Netherlands, Switzerland, Monaco to evade the tax.

In my opinion though, its all talk because to many powerful people with links to our political class don't want to upset this arrangement because they know if they can do it to Musk they can do it to anyone else they feel like going after. A lot of dirty money would probably move out of London to somewhere else.