Received from the person who taught it to you. Apparently it is meant to be taught/learnt. It was a way of leveling out all the regional accents for public school pupils. You too can have RP if you want it, it's not owned by the southerners!

It's more like a diagonal line really, as if the Fosse Way had been a fortification.

How do you feel about the phrase received wisdom, does that also stir you into anger at some invisible caricature?

Is reverse classism still classism?

Not sure where you got classism from, I've got a number of posh southern public schoolboy friends; after all, it's not really their fault that they mispronounce "butter" as "batter". What I object to is the term "received pronunciation" which implicitly places their "fwah fwah" as being in some way correct and standard.