Britain's Prime Minister David Cameron (C) speaks with military personnel as he stands between an RAF Sentinel surveillance aircraft (L) and an RAF Eurofighter Typhoon fighter jet during his visit to Royal Air Force station RAF Northolt in London, Britain November 23, 2015. Britain will invest an extra 12 billion pounds ($18 billion) in defense equipment over the next 10 years including nine Boeing submarine-hunting aircraft, Cameron said on Monday. REUTERS/Justin Tallis/pool