Perry Fellwock and CBNRC
Fascinating profile here of Perry Fellwock, who under the pseudonym Winslow Peck spilled the beans on NSA's operations to the counterculture magazine Ramparts (U.S. Electronic Espionage: A Memoir) in 1972.
Although focused almost exclusively on the activities of the National Security Agency, the Ramparts article was also the first to reveal the fact that the Communications Branch of the National Research Council (as CSE was then known) was Canada's signals intelligence agency.
References to CBNRC, but not its role, had occasionally appeared in public documents, and even in newspapers, in earlier years, and a 1960 New York Times article based on the revelations of William Martin and Bernon Mitchell, two NSA analysts who had earlier defected to Moscow, reported that Canada worked closely with the NSA on signals intelligence. But the New York Times report had not named the Canadian agency.
The Ramparts article was the first to put the two together, and Fellwock (still identified as Peck) went on to be the main source interviewed on CBNRC in the CBC documentary The Fifth Estate: The Espionage Establishment, broadcast on 9 January 1974.
It was the broadcast of The Fifth Estate (no relation to the later investigative series) that finally put the existence of CBNRC and questions about its role on the national agenda. Extensive news coverage and a series of questions about the agency in parliament soon followed.
It was only a first step. The CBNRC remained largely cloaked in secrecy even after the broadcast, and it wasn't until 1983 that the government formally acknowledged that signals intelligence was the primary mission of the agency, by then renamed the Communications Security Establishment. (The Deputy Minister of National Defence had let slip the fact that CSE did "communications intelligence" in 1977, but that statement appears to have been unplanned).
Still, the discussion that followed the broadcast almost certainly played an important role in the government's 1975 decision to move CBNRC from the National Research Council to the Department of National Defence and change its name to CSE.
And, more importantly, it marked the beginning of explicit parliamentary and media discussion of Canadian signals intelligence activities.