"Well," she replied, "if there is, you should go back and bottle it and put the fertility clinics out of business."
Unfortunately, my grandmother's water supply came from a bottomless well - all long-demolished along with their 17th century cottage, trees and hedgerows, thanks to the introduction of prairie-style farming.
So, while the idea of bottling a new form of snake oil (in this case, water) complete with ringing endorsements from the country's oldest new father has some rudimentary monetary attraction, the thought of adding yet another pseudo-elixir to an already swamped fertility induction market is a shade distasteful.
Anyway, another Briton has popped up claiming the title of "oldest father", in Yorkshire (next to fertile Lincolnshire.) His child was born while he was 78, so we're sort of on par. I say sort of, because he is way ahead of me in the "caregiver" stakes.
When I read his account and jokily commented, "wow, his pretty young wife is only 25 - there's hope for me yet" I noticed a thundery silence fell on our breakfast table.
My long-suffering caregiver finally drily suggested that with my disgusting domestic habits, I was lucky to have anyone under the age of 80 to cohabit with.
But we must make allowances for such unkindness; breastfeeding and lack of sleep must affect you once you've reached your thirties.