"This was done under secret agreements with commercial companies, described in one document as 'intercept partners'. […] some companies have been paid for the cost of their co-operation and GCHQ went to great lengths to keep their names secret. They were assigned 'sensitive relationship teams' and staff were urged in one internal guidance paper to disguise the origin of 'special source' material in their reports for fear that the role of the companies as intercept partners would cause 'high-level political fallout'."