I go into an office furniture shop to buy a swivel chair. I choose it, under the blank glare of a bored shop assistant, and go to the cash desk to pay.

I notice three credit card machines at the till.

"Oh!" I say, excited. "I can pay with a card?"

The assistant sucks her teeth at me. She half-closes her eyes to show that she is displeased. I have already said I will pay by cash and to change now would require her replacing a word on my bill with another.

"We prefer cash," she says, crawling over the words, every syllable a tremendous effort.

"I prefer to pay with a card," I say. I am, after all, the customer, I think, mistakenly.

She turns her head to the lady at the till, her eyes lingering over me as if she wishes me a painful death.

"The card machine doesn't work," says the lady behind the till.

There. That sorted that one out. Both ladies smile at me, unkindly.