I saw the 1979 BBC version when I was young and really enjoyed it, even given the lack of action. I think it was the first 'spy' thriller I'd seen which wasn't

I saw the 1979 BBC version when I was young and really enjoyed it, even given the lack of action. I think it was the first 'spy' thriller I'd seen which wasn't some sort of James Bond equivalent and I loved it for that. I still have the notes that I took while trying to figure out what was going on (we had to wait 6 weeks for the story to unfold back in the day)