The local Co-op superstore was running a magnificent offer today on a new brand of biscuits: £2.15 a box, or two for £2. I shall forbear to name the biscuits – and you’ll understand why.

Out of sheer curiosity I bought two boxes: could they really be that awful? The answer, alas, was yes. They were as hard as glass – and the very first bite broke my tooth.

But the shop had been fiendishly clever. How could I bear to throw away an unopened box of biscuits that had cost me minus-15 pence?

Be that as it may, I want my money back. When I return the box to the Co-op tomorrow I’ll give them back the 15p that’s owing, just to watch the supervisor’s face.