I had a couple of bills to pay this week which I thought would take ten minutes tops.

I took a payment slip to the post office, waited semi-patiently in the queue and handed it over with some cash. The cashier examined the slip as though they had never seen one before, and then said there would be a charge for paying it there.

I didn't quite understand why. The charge was only a couple of quid, but in principle I refused and tried the bank whose logo was printed on the pay slip.

Did I have an account with them, I was asked.

No.

That would be a charge of £10, then.

It would be funny if it wasn't so heinously unfair.

Needless to say, I declined the offer and ended up paying the bill over the phone. I don't know precisely what expense the bank in question would incur by taking my cash and paying it into one of their own accounts, but something tells me £10 is excessive.

Perhaps, it's a punitive charge – designed to discourage non-customers like myself. Either way, it ain't right.

Bank charges have been allowed to go unchecked for too long – and have been in the news again this week. Unauthorised overdraft fees of up to £35 surely do not reflect the administrative cost of bouncing or, occasionally, paying a transaction out of the goodness of their black, shrivelled-up hearts.

The problem is, nobody in the banks will own up to exactly how much it costs them. Neither will they allow a claim for a refund go to court, because they would lose. It would set a precedent and the whole system would come tumbling down, costing banks billions of pounds.

And I dread to imagine how they would set about clawing it back.