In our report of last week’s rugby match between Scotland and Ireland we wrote: “The Irish half-backs may have proven their metal…” A reader emailed to suggest that we meant “mettle”. Usually, I would say we should avoid a usage that many readers think is wrong, but in this case I think “metal” is better.

According to the Oxford Dictionary, “mettle” was another way of spelling “metal” that came to be used mainly for the figurative sense in the mid 16th century. To prove metal was to test it to verify its quality. Better to spell the figurative use the familiar way, I think, so that everyone can understand the original metaphor.

Quantity of weeks: The difference between less and fewer doesn’t usually catch us out. “Less of quantity; fewer of number,” I remember from my school days. But there are some times when a quantity sounds like a number, and last week we wrote: “Ms May has committed the Government to triggering Article 50 by the end of March, which leaves fewer than three weeks in which to pull the trigger.” As Philip Nalpanis wrote to point out, time is a quantity and the period between now and when the Prime Minister finally sends the Article 50 letter is not necessarily measured in whole weeks. It has been changed to “less than three weeks”.

In name only: My colleague Zak Thomas has suggested that we use “so-called” too often, and I agree with him. It ought to be used sparingly because, even if we are merely drawing attention to an unfamiliar word or phrase, it could be thought to imply disapproval – a value judgement that would be out of place in a news story.