Postscript

At reference 1, I drew attention to the way that high street banks make a lot of their money by punishing errors in financial management.

So today, in a rare computer error, HSBC sent me a second copy of my credit card bill, a few days after they sent me the first. I can't remember when I last noticed an error in their communications with me.

But in the course of checking that the second copy was indeed identical to the first, except as regards things like batch number, I noticed that the interest charged on anything carried over to next month is 16.9%, compared with the 0.3% or so they might offer me on a deposit account. I also came across the table snapped above - in which the rates look truly punitive - unless you are lucky enough to qualify as a student. Towards the end of 50 pages of terms and conditions, so maybe not all readers get that far.

It may also have been that the 16.9% interest rate was highlighted in the second copy in a way that it was not in the first. But the second copy has now gone through the mincer on its way to the compost bin, so I shall never know.

PS: maybe someday someone will explain to me how the difference arises between the annual rate and the effective annual rate.

Reference 1: https://psmv4.blogspot.com/2021/03/bank-job.html.