Continuity mistake: In the scene by the fountain from Briony's point of view, when Cecilia takes her top off she pulls the strap of her undergarment twice. However, from Robbie's point of view, she doesn't pull the straps at all.
Continuity mistake: In the first enactment of the fountain scene from Briony's viewpoint, the twins have just left her room and can be heard yelling downstairs for Celia's permission to go swimming. In an immediate, steady shot she goes to the window and witnesses the fountain scene already midway through. As we see in the next scene, from Celia's perspective, the twins run by asking to go swimming and she lingers in the piano room for several minutes and takes even a few more minutes chatting and walking with Robbie before they even begin the fountain scene.DJ Vander Schaaf