Reactor viewing galleries?

During my research, I managed to walk inside a handful of nuclear power reactors. Then 9/11 came along and ever since then, or so it seems to me, security at these power plants is so tight that visiting now would be impossible. So I was bemused to read British pioneer Christopher Hinton in a 1957 letter:

One of the things that I regret in the design of Calder Hall is that we did not take account of the immense public interest in the Station when it was being designed. Had we thought of this I should have provided galleries through which parties of non-technical visitors could move and see the Plant without having any access to working sections.

Hinton, Christopher. 1957. Hinton to Cunningham, Mar. 28, 1957. AB 19/89. National Archives, Kew, United Kingdom.
Hinton letter