150715-N-AT895-174 LONDON (July 15, 2015) Chief of Naval Operations (CNO) Adm. Jonathan Greenert, center, answers questions during a moderated talk focused on the future of the British-American naval alliance at Chatham House, the Royal Institute of International Affairs. With Greenert are Dr. Patricia Lewis, PhD., left, research director for international security at Chatham House, and First Sea Lord of the Royal Navy Adm. Sir George Zambellas. Chatham House is an independent policy institute based in London. (U.S. Navy photo by Mass Communication Specialist 1st Class Nathan Laird/Released)