Does the Queen speak the Queen's English? Not to the extent that she did at the beginning of her reign, is the answer. The Queen's accent has changed over the decades - she no longer says the traditional 1950s 'posh' pronunciation 'orf' (off), 'bleck het' (black hat) and 'syuper' (super), and her vowels have been influenced by Estuary English. So says lexicographer Susie Dent in a Daily Telegraph article.
These days a regional accent is equated with honesty and reliability, which explains why politicians affect them. Another big change -- in grammar this time -- is the trend towards using the active voice rather than the passive in official documents (tax forms now say 'I have sent you two forms', rather than 'you have been sent two forms' or 'two forms have been sent to you').
Things that were once considered incorrect, such as saying 'disinterested' when you mean 'uninterested', are now very common.
Minority communities are adding new words to English eg bait (absurd), bare (lots of) and safe (a greeting) from Caribbean English. Hinglish is responsible for adding Hindi- and Urdu-derived words to the language.
Here's the full article.