Jonnie Robinson, Curator, English accents and dialects, British Library Sound Archive, writes:
Contrary to popular opinion everybody speaks with an accent. We would probably struggle to place these speakers geographically, but the way they speak nonetheless reveals something about their social and educational background. They speak with an instantly recognisable accent: Received Pronunciation (RP), commonly - but increasingly misleadingly - referred to as BBC English. RP is the proper name of the regionally non-specific accent perhaps most readily associated with speakers from public school backgrounds. It does, however, encompass a wide variety of speakers and should not be confused with the notion of 'posh' speech. RP is best considered as the accent on which teaching English as a foreign language is based.
People's attitudes towards individual dialects or accents are purely subjective. Unfortunately, some dialects of English have historically been viewed more positively than others and individuals often suffer as a result of irrational prejudice against the way they speak. It's important to stress that, from a purely linguistic point of view, no particular dialect is better at communicating meaning than another. The fact that prestigious or highly regarded forms exist is more a reflection of value judgements based on social, rather than linguistic, criteria.
In the immediate post-war period, as social mobility became possible for increasingly larger numbers of people, many speakers felt a regionally non-specific accent was highly desirable in order to move up the social ladder and indeed vital to retain that position of privilege. In recent years, as these speakers seem to suggest, this appears somewhat anachronistic and we seem to be a little more tolerant of variety and more willing to embrace the wonderful diversity of spoken English. In an increasingly homogeneous society, the vocabulary, structure and sounds that define the speech of a particular region, should be and indeed are for many speakers, a source of great pride and an important expression of cultural identity, as is illustrated by the positive attitudes these speakers feel towards linguistic variety.