I came back home today to an unhappy find.
"Snowball of X to the Minus One" was laying quite still in a place, in his 16+ years, I've never seen him sleep before, only then to notice a trail of urine behind him.
He can't really move much and cries when I try to comfort him.
Sadly my experience with cats tells me that his condition will not improve.
I will be putting him down tomorrow.