I cannot quite believe how many criticisms I can make in response to the question from your former colleague, Dominic Grieve.
1. How on earth can you justify saying that the loan charge is "plainly" not retrospective?
It requires you to ignore what the ICAEW have repeatedly said since 2016: ion.icaew.com/taxfaculty/b/w…
The ICAEW also noted that the proposals "contravene generally accepted notions of fairness".
Thus, perhaps, on balance Mr Grieve is in good company and his views ought not to be surprising.