F900 Ex, thank you for your comment....the decision was in fact made for me by the doctors as the stroke was a consequence of an operation on a dodgy knee (got trapped between two yachts on the Solent ten years before).
Otherwise it is very likely as I was instructing in a gliding club, that the Chief Flying Instructor would have been told by other members that the old woman was starting to lose it, and he would have had a quiet word. Clearly the brain is still working to an acceptable standard, and as mentioned before, women last longer than men. In a club environment the gossip gets round so a pilot with a problem is more likely to get noticed.
The knee, I am pleased to report, works beautifully.