History of the Examination Unit
The Examination Unit was Canada's first code-breaking agency. Hidden within the National Research Council, the XU, as it was typically known, operated from 9 June 1941 until its dissolution in August 1945, in the final days of the Second World War.
Canada had monitored U-boat transmissions and other signals intelligence targets from the very beginning of the war (and even to a limited extent beforehand), but it was the creation of the XU that opened the way for high-level SIGINT cooperation between Ottawa, London, and Washington and thus laid the groundwork for Canada's participation in the post-war Five Eyes intelligence-sharing community.
As its activities were winding down, an internal, classified history of the XU was compiled under the editorship of Gilbert deB. Robinson. (More on Robinson here.)
That highly secret history remained hidden from the public for many decades, but eventually a redacted version was released following an Access to Information request. I obtained a copy of it shortly afterwards, in 1991.
Now you can read it here:
G. deB. Robinson (ed.), A History of the Examination Unit: 1941-1945, Examination Unit, July 1945.