The language in this passage is so specifically chosen and so carefully set that it very nearly takes my breath away (do allow me a little hyperbole). It's precisely the words that they tangle over, still, right up to the end, the words tying heart to mind, that are critical, his asking for consent and her giving it. I've read this ending a hundred times, but it's only today that I realized the most important word in it is desperately, which she uses to test him—or not to test, I suppose, more to measure, or weigh, or at least get to the bottom of what he's offering and what he expects from her—because desperation is what she fears most. Desperation turns you over to the Annie Wilsons and, worse, the Philip Boyes of the world, it's what gets you tossed in the can sooner or later, or at least stops your mind from functioning while your heart leads you around by the nose. And so it's his no to that question that finally allows her to say yes to his, and the fact that they both reject what any typical fictional romance would, almost by definition, cling to.
Anyway, don't read! If you've never read it, I mean. The end of Gaudy Night:
The final Chorale was sung, and the audience made their way out. Harriet's way lay through the Broad Street gate; Peter followed her through the quad.
"It's a good night—far too good to waste. Don't go back yet. Come down to Magdalen Bridge and send your love to London River."
They turned along the Broad in silence, the light wind fluttering their gowns as they walked.
"There's something about this place," said Peter presently, "that alters one's values." He paused, and added a little abruptly: "I have said a good deal to you one way and another, lately; but you may have noticed that since we came to Oxford I have not asked you to marry me."
"Yes," said Harriet, her eyes fixed upon the severe and delicate silhouette of the Bodleian roof, just emerging between the Sheldonian and the Clarendon Building. "I had noticed it."
"I have been afraid," he said simply; "because I knew that from anything you said to me here, there could be no going back. . . . But I will ask you now, and if you say No, I promise that this time I will accept your answer. Harriet; you know that I love you: will you marry me?"
The traffic lights winked at the Holywell Corner: Yes; No; Wait. Cat Street was crossed and the shadows of New College Walls had swallowed them up before she spoke:
"Tell me one thing, Peter. Will it make you desperately unhappy if I say No?"
"Desperately? . . . My dear, I will not insult either you or myself with a word like that. I can only tell you that if you will marry me it will give me very great happiness."
They passed beneath the arch of the bridge and out into the pale light once more.
She stood still; and he stopped perforce and turned towards her. She laid both hands upon the fronts of his gown, looking into his face while she searched for the word that should carry her over the last difficult breach.
It was he who found it for her. With a gesture of submission he bared his head and stood gravely, the square cap dangling in his hand.