Chatham House Rules

"Under the Chatham House Rule, anyone who comes to a meeting is free to use information from the discussion, but is not allowed to reveal who made any comment. It is designed to increase openness of discussion. The rule is a system for holding debates and discussion panels on controversial topics, named after the headquarters of the UK Royal Institute of International Affairs, based in Chatham House, London, where the rule originated in June 1927." - Chatham House Rule (Wikipedia)