Difference between Head of State and President
LONDON, ENGLAND – APRIL 24: British Prime Minister David Cameron (C) talks with actor Brian Blessed (R) prior to Blessed attending a photocall organised by the National Anti-Vivisection Society on “World Day for Laboratory Animals” in which a post card signed by celebrities in support of greater transparency on animal research will be delivered to 10 Downing Street on April 24, 2013 in London, England. (Photo by Tim P. Whitby/Getty Images)
 talks with actor Brian Blessed (R) prior to Blessed attending a photocall organised by the National Anti-Vivisection Society on "Pin It")