Aylmer, with his precise, thin voice, sounded like a pedagogue (and in real life did some studies that he published - like his book "The Drood Murder Mystery"). He actually did play teachers. In "Edward My Son" he is the house master who is blackmailed by Spencer Tracy into forgetting about expelling Tracy's selfish, trouble making son. But he could play doctors ("The Doctor's Dilemma", "The Citadel"), lawyers or Judges ("The Chalk Garden"), or other professionals. All of these film roles were supporting parts. He gave his all to his roles - like in "Separate Tables", when he is at first fairly neutral to Gladys Cooper's efforts to drive David Niven out of the residence hotel they reside in, but slowly gets fed up with her highhandedness and leads the switch of the other residence against Cooper's wishes.
But here he is the title character - sent to get in touch with the daughter of an old friend who has not left her native Germany. But Aylmer is a Jewish gentleman, and one who barely understands what is going on in Nazi Germany. He heads there, aware that there is some degree of anti-Semitism (when hasn't there been that), but not realizing it's virulence. Gradually he is made aware of it, due to his sloppy handling of his mission, and also that, although he is a naturalized English citizen the German regime is more than willing to overlook that point.
He ends up mistreated, humiliated, and imprisoned in a 1930 style concentration camp (which shows that they were known before the creation of "the final solution). Aylmer's key scene in all this is when one of the few local Jews who was willing to advise him, is taken out of a nearby cell, his face showing a degree of fear and horror that is unimaginable. Aylmer, looking through the bars of his cell door, and dozen of other prisoners yell defiance at the butchers who will shortly kill this poor man.
One thing about the story that was particularly interesting is the character of Elsie Silver. Elsie is Jewish, but never emphasized that part of her history. In fact, when Emmanuel tries to contact her she is annoyed that he's raking up her past. And with reason - her boy friend is a high ranking young official in the S.S. It is rarely mentioned, due the incredible story of torture and evil practiced on the bulk of Germany and Europe's Jews by the Nazis and their allies, that there were "quislings" among the Jews as among other groups. Maybe "quislings" is too harsh, but protected exceptions is not too harsh.
The most notable example of Jews who were not bothered were in France and Italy. Gertrude Stein, who was Jewish and American, was such an important figure in the world of French cultural circles she was let alone. So was Bernard Berenson the Renaissance art expert (whom Mussolini's regime did not bother). On the other hand, the Jewish French Historian Marc Bloch joined the underground, was captured, and tortured to death. The German, Stephan Zweig, fled to Latin America, and committed suicide because of the hostility and indifference he met abroad.
Therefore the picture of Elsie's special relationship to the regime is unique for 1944 in any movie. I doubt if it would have occurred in an American film of the period (although in "The Pied Piper", Monte Wooley does find that Nazi officer Otto Preminger wants him to get his half-Jewish niece out of the continent to England - Wooley does do it). But an Elsie Silver was too hard to swallow, as rumors of massive slaughter began to come through. By 1945 it would have been next to impossible to discuss it.
For an early, and good view of the state of horror in Nazi Germany for the Jews, and for the performances of Aylmer and Greta Gynt, I give the film a 10.