According to Wikipedia this is “..a form of cant slang used in Britain by actors, circus and fairground showmen, merchant navy sailors, criminals, prostitutes, and the gay subculture.”

It died out in the 60s naturally though assisted by the view, as homosexuality was decriminalized in the UK, that there was no need to hide anymore.

Those were the days, when people happily abandoned linguistic affectation in order to join the mainstream..

Anyway, here is a short film entirely in Polari. See if you can understand it.