A Quadripartite Agreement is a treaty between four states or four commercial parties. The most famous Quadripartite Agreement is that of the Four Power Agreement on Berlin of September 3, 1971 between the United States, the Soviet Union, the United Kingdom and France. Another one was that on intelligence matters between Britain, the United States, Canada, and Australia, of 1947. This was a secret treaty, allegedly so secret that it was kept secret from the UK Prime Minister. The treaty gave each nation access to almost all of the intelligence gathered by the others, especially signals intelligence. This was of great advantage to Canada and Australia, which did not have the infrastructure to gather much of their own intelligence. While the raw intelligence is shared, each nation insists on doing its own analyses, and sometimes different nations would come to different conclusions based on the same data. Controversially it has also been alleged that the treaty has been used to bypass rules against domestic spying, by having foreign allies do the actual gathering. For instance the Canadian Communications Security Establishment was reportedly used to spy on enemies of Margaret Thatcher. It was superseded by the UKUSA agreement.
