Simon Langton's 1987 Whistle Blower is a good solid counter-espionage film. Netflix estimates I will like it to the extent of 3.2 stars out of 5 — about a 50-50 shot. And I did like it — I'd give it at least a 4.
That is, until John Gielgud's last big speech, which (along with some other phrases in another character's mouth) I recognized as coming straight out of the 1974 novel Tinker Tailor Soldier Spy. That was some disappointment — really turned me off the movie.
But Netflix doesn't have a way of registering this sort of nuanced reaction to a movie: enjoyed it until I recognized something that, at a minimum, was neither original nor, it seems, explicitly attributed.