People are understandably amazed that an envelope, marked only with the name and address of a friend, can travel from their local postbox in West London across many hundreds of miles to the other side of the country, where it is deposited gently by a postman through a letterbox — amazed because the friend to whom the letter was addressed also lives in West London.

This might explain your gratitude when a letter arrives safely at its destination, without having been mis-delivered, or dumped over a hedge by a postman keen to get home early, or roughly handled by a postal worker who thought that the sticker marked “Fragile” simply meant that the parcel should on no account be drop-kicked across the sorting office, but that a gentle toss to a colleague 20 yards away wouldn’t do the package’s contents any lasting harm.

When you have a competent postlady, as I currently have, the mail system is a marvel of efficiency, and not especially expensive for all that is involved. So you are right to think it unethical to re-use an uncancelled stamp, the Royal Mail having met its part of the bargain.

It is no different from not alerting a shopkeeper to the fact that he has handed you too much change. The Royal Mail may have decided it was more important to expedite the delivery of mail than to risk any delay by confirming that each stamp had been rendered unusable. It seems churlish to profit from a situation that may have arisen as a result of the firm’s diligence.