I just re-read The Fashion in Shrouds, first published in 1938. The first thing that struck me was the simple phrase "sickening deterioration" that Allingham uses to describe the feeling that one gets when one's love is gradually losing interest and one knows it. Perfect.
And how about this, a paragraph that appears near the beginning of Chapter 8 after an embarrassing scene at a restaurant:
It was a comic moment but it passed too soon, leaving only a growing sense of embarrassment as half-a-dozen diners at other tables swung round to stare with that insolence which comes from an attempt to look casual, or perhaps invisible, before they returned to warn their companions not to look round immediately.
Insolence. Without that word, I suspect the paragraph would not have caught my eye. I certainly wouldn't be telling you about it. But its presence made me stop and read the passage through a couple of times, relishing the aptness of the description.