"In the last 40 or so years, there have been dramatic changes to the social class structure in Britain and to a certain extent this is reflected in pronunciation." - seems obvious..
"It demonstrates that the monarchy, at least as far as the spoken accent is concerned, isn't isolated from the rest of the community." - to read more click on the below link:
But if you are more empirical than theoretical, just listen to that:
Spotted the difference?
RP (received pronunnciation) - the pronunciation of British English considered to be least regional, being originally that used by educated speakers in southern England.
Standard English - English spoken with a 'standard' pronunciation which corresponds to the pronunciation given in a dictionary.
"It is important not to confuse the notion of Received Pronunciation, as a standard accent, with the standard variety of the English language used in England that is given names such as "Standard English", "the Queen's English", "Oxford English" or "BBC English". The study of RP is concerned exclusively with pronunciation, while study of the standard language is also concerned with matters such as grammar, vocabulary and style."
Be careful with your RP pronunciation just not to sound too posh. Otherwise, you'll simply sound ridiculous and nobody wants that, right?