In reply to jonny taylor:
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> Tarr knew who the mole was, did he not,
He knows there's a mole but not who it is
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> When Peter leaves with the day log, someone passes him on the stairs whistling a significant tune (I actually missed who it was, but I don't think it was the mole). Why were they listening in on his phone call? Was it just general paranoia with everybody suspicious of everybody else?
Just paranoia unless there's a change from the book!
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> A throwaway scene that I did not get at all - Smiley tells Peter to tie up his loose ends, or something like that, and he throws out his "lodger". Why?
Because at the time being of a particular orientation was a major problem; it was seen by those responsible for vetting as a major weakness and not good for one's career. I don't remember this from the book...