The government has today published a House of Commons Library Briefing Paper (No. 4369) on the topic of “Retrospective Taxation” which describes, inter alia, the practices which successive Parliaments have adopted in relation to the enactment of tax legislation having retrospective effect.
The paper may be found here: https://researchbriefings.parliament.uk/ResearchBriefing/Summary/SN04369
The paper makes reference to the decision of the High Court in the case of Cartref & Others v HMRC  WEHC 3382 (Admin), which was the subject of an earlier post. The High Court ruled that the Loan Charge is compatible with human rights.