RUISLIP, ENGLAND - NOVEMBER 23: British Prime Minister David Cameron talks with soldiers from the Royal Welsh Infantry as they stand in front of a Lockheed Martin Warrior Infantry Fighting Vehicle during his visit to Royal Air Force station RAF Northolt at RAF Northolt on November 23, 2015 in Ruislip, England.  According to a government statement Mr Cameron is set to promise an additional 12 billion GBP to strengthen the defence forces, when he presents his government's Strategic Defence and Security Review to parliament later today.. (Photo by Jack Hill - WPA Pool/Getty Images)