I still don't know the answer to this but I do know, quite categorically, what the answer isn't.
And that is 49.
As I have already demonstrated this week, to my very considerable cost.
Prompted by a rather urgent need to muse upon this and others of life's mysteries, I headed waterwards, only to find - of course, this week's high tides again, silly (not wise) me - that my rickety old 'thinking jetty', aboard which I have privately mused, with many a hot chocolate for company, since arriving on the Muddy Isle, was completely submerged. Bother. So I went for a trudge on the beach instead but was too lost in thought to take any pics.