LONDON, ENGLAND - MARCH 03: British Prime Minister David Cameron (R) bows as he greets Queen Elizabeth II during a ceremonial welcome for the State Visit of The President of The United Mexican, Senor Enrique Pena Nieto and Senora Rivera at Horse Guards Parade on March 3, 2015 in London, England. The Ceremony marks the start of a three day visit to Britain. (Photo by Toby Melville - WPA Pool/Getty Images)
