Chatham House Rule

Chatham House Rule from Wikipedia:

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 particular 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.

The rule was created in 1927 and refined in 1992. Since its most recent refinement in 2002, the rule states

When a meeting, or part thereof, is held under the Chatham House Rule, participants are free to use the information received, but neither the identity nor the affiliation of the speaker(s), nor that of any other participant, may be revealed.

Sometimes the reference is made to Chatham House rules. However, Chatham House states that the singular should be used as there is only one rule.

The rule is designed to promote openness of discussion of public policy and current affairs, as it allows people to express and discuss controversial opinions and arguments without suffering the risk of stalling their career or even dismissal from their job, and with a clear separation from the opinion and the view of their employer.