HMRC work to rules set by the government so it is the government that need to ensure that the rules are fit for purpose. Part of the EU shake up of taxation rules mooted before 2016 was to close the tax loopholes that resulted in the mega rich being able to stash their earnings where HMRC could not get at them. If you have any doubt as to that is why those in power conned people into voting to leave the EU then you need to work on your comprehension skills.