Good movie!
If you ever get the chance to see this old WWII movie, then make the most of it... you'll be glad you did!
Experience is something you don't get until just after you need it!
One review on IMDb suggests that the Ralph Richardson character at first calloborates with the Nazis and only decided to go against them when he heard a children's rhyme being sung at a school.
In fact, at the beginning of the film he was given a few hours by the Gestapo chief (who was depicted as a comical idiot by Esmonde Knight) to decide whether or not he wished to help the occupiers.............with or else clearly the other option.
It was whilst making up his mind that he heard the children's rhyme as he waited to collect his young son from school.
An unusual feature of this film is that the ending was clearly depicted in the opening shots and the rest was flashback.
This movie was recently released on DVD (in case anyone's interested) and I bought my copy a few weeks ago.
Experience is something you don't get until just after you need it!