At the end of World War II five nations that’d built up intelligence-gathering links during the conflict agreed to pool their capabilities and signed up to the 1946 UKUSA Agreement to formalise the relationship going forward.

The five signatories to the classified agreement were the United States, United Kingdom, Canada, Australia and New Zealand, who entered into the world’s oldest and most-established snooping collaboration to establish formal cooperation on signals intelligence.

The alliance grants member countries the right to swap information gathered by their national intelligence agencies and, while signals intelligence remains the foundation of the relationship, it has expanded to include areas such as cybersecurity, counterterrorism, human intelligence and geospatial intelligence... FULL STORY