From The Mother Tongue: English and How it Got That Way by Bill Bryson:
A paradox of accents is that in England where people from a common heritage have been living together in a small area for thousands of years, there is still a huge variety of accents, whereas in America, where people from a great mix of backgrounds have been living together in a vast area for a relatively short period, people speak with just a few voices. As Simeon Potter puts it: “It would be no exaggeration to say that greater differences in pronunciation are discernible in the north of England between Trent and Tweed [a distance of about 100 miles] than in the whole of North America.
And on page 109:
Professor Higgins boasted in Pygmalion that he could place any man in London within two miles, “sometimes within two streets.” This isn’t as rash an assertion as it sounds. Most native Londoners can tell whether someone comes from north or south of the Thames. Outside London even greater precision is not uncommon.
It’s hard to stop with just a couple of short quotes. This is a fascinating and highly entertaining book. It even contains a chapter about swearing. And yes, it does have all those really bad words in it.
~ ~ ~