sanmac, You have been duly exposed to one of the world's strangest quirks, a uniquely British one (nowhere else at all). Many people in the UK have no mental connection to body weight beyond the stones concept, and this is even though the metric system was introduced around 50 years ago and the vast majority of people were raised within it (yeah, sure - there was the Brexit type resistance against that, foreign nonsense it is, etc.). They can often relate to the weight of other things in kilos, such as bags of cement, sand, parcels, baggage, etc. but not body weight, even at around 3kg for a newborn.
There are lots of people who will tell you that they have lost half a stone - presumably some have now given up hope of finding it, they can never describe it so I can help them look for it. Do you know what half a stone might look like, I don't ?