Symbolism in Tinker, Tailor, Soldier, Spy (open spoilers)

Did anyone else notice how many scenes featured windows?
I wasn’t counting, but I’m guessing that 20-30% of the shots consisted of someone being viewed through a window, or looking out a window, or silhouetted against a window.

They’re on the inside, we’re on the outside. Etc.

I just watched this, and noticed it as well. It was particularly striking in scenes at the Circus, and outside Smiley’s impromptu office. My perception as I watched was that it was intended to create a persistent feeling of being exposed.