This is much harder to evade - if you own most of Mayfair, you can't just move your assets elsewhere - they are very clearly tied to the location.
Of course, this would mean taxing powerful aristocrats, including the royal family. With their large majority, the British government had the opportunity to do this, but decided to take an easier path. The reason why this path was easier is now becoming clear to them.
Simple, and more effective!
Hell even Switzerland taxes global assets. You just declare your stocks, property, etc at some instantaneous value and that’s that. Capital gains aren’t taxed.
The system is easy to cheat and until recently it was possible for HNW people to get a bespoke deal when moving there. But the tax rate is low enough and the risk is high enough that it’s more beneficial to just pay.