Britain's Prime Minister David Cameron (C) walks with Group Captain David Manning (R) past an RAF Eurofighter Typhoon fighter jet and a Royal Navy Wildcat multi-role helicopter 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