I did look at the Wikipedia and another article on RP. I base my statement on what my speech teacher in London, Andrew Jack from LAMDA, said was the origin of RP. Yes, there are plenty of accents in the UK who would be received by the Queen - from Scotland, Wales, Northern Ireland, etc. I meant it more in a colloquial way, such as a refined speech, later adopted by the BBC, that serves as a kind of standard; an equivalent here would be the standard American speech that was adopted by tv and radio broadcasters in America on network (not regional) broadcasts. Someone preparing to do Eliza would be coached in RP and/or something between RP and something a bit more upscale or "posh". Julie Andrews had to be coached in Cockney for her pre-transformed Eliza, but her more "lady-like" Eliza seems to be more like her natural speaking voice, which is as standard English as one might point to as practically a paragon.