The official list of UK bank holidays includes a 'Platinum Jubilee' holiday scheduled for 3 June 2022 to mark the start of Queen Elizabeth's 70th year on the throne.
There is, naturally, some possibility that Queen Elizabeth's reign ends before this milestone is reached. If this were to occur, is there any provision to enable the cancellation of the proposed holiday? At what point does it become guaranteed?
Bank holidays can be created or moved by a royal proclamation. In this case, a royal proclamation was used to move the statutory Spring bank holiday to early June. Another royal proclamation could reverse this. There is no limit to when such a change can be made. So in theory it could happen at any time. No act of Parliament is needed.
In practice, even if the Queen dies, the bank holiday will remain (as a memorial weekend or something)