if you're thinking U vs non-U it was mid-XX, and a bit of a U joke[0] that non-U peeps took way too seriously.

I wonder: has anyone made a list of all the different ways we Sneetches have besides our bellies, to distinguish in- and out-groups?

https://en.wikipedia.org/wiki/U_and_non-U_English

[0] when Jilly Cooper shows up in the References of a Wikipedia page it's all a bit of a lark