Re: I don't understand the negative comments about the "jokes"?
"Which squirrels?"
They'd have to be red squirrels.
Truth is though there probably were never many around......red squirrels like conifers, not deciduous trees, and London (and southern England in general) was never exactly rich in Scots Pine. People blame the lack of reds on the rapid expansion of the greys, but the truth is that there were probably never that many reds around anyway: the environment wasn't there.
FWIW my uncle was supposed to have had the last red in Somerset as a pet - when it died in the 1950's it was stuffed and displayed at the local primary school