Two quibbles
I realize its absurd to trifle with a classic more than 70 years old and the problems do nothing to diminish my admiration for the film but there are two issues that nag.
Of lesser importance is the fact all it takes to keep two woman quiet is just to wrap their faces in gauze.
More important: Iris, Charters and the woman known as "Mrs." Margaret Todhunter are left behind in the dining car with the fake officer who has a gun on them as the nun slips away to change tracks. The nun switches the track, the train heads off, the bad guys are left behind.
The next we see of any of the dining car hostages is back in London at Victoria Station. Caldicott and Charters learn their precious cricket match has been cancelled and Iris and Gilbert are about to walk into the sunset following a stopover at the Foreign Office.
So my question is this: What the hell happened to the "officer" with the gun and how did the three escape from him? It's never explained.
BTW, isn't Margaret Lockwood GORGEOUS?