Members of Parliament are seen attending a session of Parliament in the House of Commons, called to discuss the Syria crisis, in this still image taken from video, in London August 29, 2013. Cameron said on Thursday it was “unthinkable” that Britain would launch military action against Syria to punish and deter it from chemical weapons use if there was strong opposition at the United Nations Security Council. REUTERS/UK Parliament via Reuters TV (BRITAIN – Tags: MILITARY POLITICS)