In retrospect, one of the things that you really have to appreciate about le Carré is his steadfast refusal to keep a character alive longer than is realistic for purely narrative purposes. The same cannot be said for this little Michael Caine vehicle, which spent two thirds as a dry and competent thriller (nothing amazing, but a combination of servicable performances and servicable plot) and then spent the last third as a poor imitation of the James Bond films it tries to surpass: a cartoonish villain with hypnosis, a suddenly Herculean protagonist, and a climax that tries very hard not to answer "wait, why didn't they just kill this guy?"
I try not to let rough endings spoil my enjoyment of a film; it was hard to do that with this one, because the left turn feels so jarring that it spoils your taste of what came before.