Pathe News – Greenwich

There were windows in there back in the day too if I’m not mistaken

No, you're not mistaken... they are still there! Some are covered by display cases and others have shutters over them. There are windows all around, which you can see clearly from the outside:

(the top set of windows in the above image)

The fashion for windows clearly waned when the domes at Herstmonceux were built. I don't think any of the domes had an external window. Many historic observatory domes had windows, but I'm not aware of any post-WW2 observatories with this design... an interesting little research project for somebody!

Of course!!! Looking at the building from another perspective would answer my question!

I've looked into it a little… Will start a new topic as we're diverging into architecture.