I have my doubts I should have been there, but the creaky old stairway that looked not very safe was no longer blocked off (probably due to some work being done on the weekday, by the looks), and there was no one around. So I had a look in this roof space area that I'm not sure has ever been open to the public. (Maybe it was when it used to be used for something else. And I do have childhood memories of its former use. But now that I think of it, the handrail you can see in one photo looks fancy enough that it used to be for public access. And why put a nice big stained glass window in if it couldn't be seen by the public? So yes, I think it probably was formerly open, but hasn't been for a long time.)
The very observant reader of this blog may know which Brisbane building I refer to.