I still can't understand how Cecil and my old tutor, Fitz, got along so well, when we often called Fitz "the Genius" and avoided calling Cecil anything at all, so as not to be rude.
-- Briony Larkin (chapter 8)

Importance: This quote has it's importance in determining Briony and Cecil's backstory, how they both studied together and also the massive difference between their intelligence levels. This is why Briony is unable to be attracted to him, despite his physique. It is important when Cecil attempts to make a move later in the novel, and is rejected.

We laughed a lot and I grew warmer still, lovely and warm. I do realize that some of that warmth was due to the wine, but there was much more to it than that. There are two distinct aspects to Communion wine: one aspect is the wine itself, the other is the idea of communion. Wine is certainly warming...
-- Briony Larkin (chapter 15)