Cecilia's reaction to the letter. What makes it funnier is that Briony casually hands it to her unwrapped, Cecilia takes one look at it and demands to know if Briony has read it already.
Then there's Robbie telling Cecilia that the letter is a mistake.
Robbie: [The other letter] was more formal and less...
Cecilia: Anatomical?
When the vase handle breaks and falls into the fountain, Keira Knightley's delivery of "Oh you idiot!" is priceless.
Cecilia: You realise that's probably the most valuable thing we own!
Robbie: (chucklig) Well not any more it isn't.
Thomas Nettle describing the situation quite nicely.
"No one speaks the fucking lingo out here. You can't say 'pass the biscuit' or 'where's me hand grenade?', they just shrug. Cause they hate us too. I mean, that's the point. We fight in France and the French fucking hate us. Make me Home Secretary and I'll sort this out in a fucking minute. We got India and Africa, right? Jerry can have France and Belgium and whatever else they want. Who's fucking ever been to Poland? It's all about room, Empire. They want more empire, give 'em this shithole, we keep ours and it's Bob's your uncle and Fanny's your fucking aunt! Think about it."
in The Graham Norton Show, the filming of the library scene was made no less awkward by the director yelling, at one point: "Keira! Wank him off!"