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.
Received Pronunciation
Like all accents, RP has changed with time. For example, sound recordings and films from the first half of the 20th century demonstrate that it was usual for speakers of RP to pronounce the sound, as in "land", with a vowel close to , so that "land" would sound similar to a present-day pronunciation of "lend". RP is sometimes known as the Queen's English, but recordings show that even Queen Elizabeth II has changed her pronunciation over the past 50 years, no longer using an -like vowel in words like "land". 
Some changes in RP during the 20th century include:The change in RP may be observed in the home of "BBC English". The BBC accent of the 1950s is distinctly different from today's: a news report from the 1950s is recognisable as such, and a mock-1950s BBC voice is used for comic effect in programmes wishing to satirise 1950s social attitudes such as the Harry Enfield Show and its "Mr. Cholmondley-Warner" sketches.