Christopher Mabbutt, Poirot and others in “Unfinished Business”

The irony is, Lieutenant, it's in our country's interests to have peace with Germany, to stop the Communists creeping ever westward. We are patriots who pass information to Hitler because if Chamberlain's policy of appeasement doesn't hold and someone like Churchill gets his hands on power, we will be dragged into a war a hundred times worse than the last one. And in that scenario, the quicker Germany knocks out a weak liberal England, the better for all Europe.

Poirot

Or what would remain of Europe under the Nazis. Monsieur, you have not seen your country overrun by foreign tyranny. I have. And I tell you, monsieur, that I value the "weak liberal England," as you call it, as a country well worth the fighting for.

But you won't do the fighting, will you, monsieur? It will be the young boys again. And if I can save one life by keeping this country weak so it cannot engage in war with Germany, then I will be proud of what I've done.

Fiona Hanbury had a life.

I think people like that are called collateral, Lieutenant. They die for a greater good.