Green’s Dictionary of Slang

smart, upper-class .

1993		Times 1 Oct. 19/4: He decides that I have a posho voice which he jestingly mimics. ‘Oh soopah, wonderful actually. Does one want more coffee? Would one want any sugar?’.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 202: ‘I reckon even with his posho parents Pig Iron Bob is nothing but a dead-set hay-pirate’.
2000		N. Griffiths Grits 69: Eyr some posho English cunt’s private erd.
2019		Twitter 30 May 🌐 I still prefer Alex Glasgow’s original, complete with parody posho accent.
2023		M. Herron Secret Hours 25: ‘Get seen hobnobbing with the likes of me, your posho neighbours’ll have you tarred and barrelled’.