LONDON, ENGLAND - JULY 13:  Downing Street staff listen to Prime Minister David Cameron speaking as he leaves Downing Street for the last time on July 13, 2016 in London, England. David Cameron leaves Downing Street today having been Prime Minister of the United Kingdom since May 2010 and Leader of the Conservative Party since December 2005. He is succeeded by former Home Secretary Theresa May and will remain as Member of Parliament for Witney in Oxfordshire.  (Photo by Dan Kitwood/Getty Images)