London
There are many accents traditionally associated with London. The most well known of the London accents long ago acquired the Cockney label from London's East End, which is heard both in London itself, and across the wider South East England region more generally. The accent of a 21st-century Londoner varies widely; what is becoming more and more common amongst the under-30s however is some fusion of Cockney with a whole array of ethnic accents, in particular Caribbean, which form an accent labelled Multicultural London English (MLE). The other widely heard and spoken accent is RP (Received Pronunciation) in various forms, which can often be heard in the media and many of other traditional professions and beyond, although this accent is not limited to London and South East England, and can also be heard selectively throughout the whole UK amongst certain social groupings. Since the turn of the century the Cockney dialect is less common in the East End and has 'migrated' east to Havering and the county of Essex.
American English
In 2010, William Labov noted that Great Lakes, Philadelphia, Pittsburgh, and Western accents have undergone "vigorous new sound changes" since the mid-nineteenth century onwards, so they "are now more different from each other than they were fifty or a hundred years ago". However, a General American sound system also has some controversial degree of influence, for example, gradually ousting local accents in urban areas of the South and at least some in the Inland North. Rather than one particular accent, "General American" can be defined as any American accent that does not incorporate features associated with some particular region, ethnicity, or socioeconomic group. General American features are embraced most by Americans who are highly educated or in the most formal contexts, and regional accents with the most "General American" native features include North Midland, Western New England. and Western accents. Typical General American features include rhoticity, the "father–bother" merger, "Mary–marry–merry" merger, and pre-nasal "short "a"" tensing.