In a compartment on a train after their visit with the writer Southgate, Diana and Robert kiss. Both of Robert's hands touch her face in a close shot. When the angle changes to a shot from the corridor looking into the compartment, they are still embracing but Robert has a cigarette in his right hand which is resting on his knee.
When Robert and Diana are throwing things into the river, the tide is fully out. They see the derelict house, go and investigate and then discuss it outside again, when the tide is fully in.
When Diana mounts the motorbike the night after Prince Cesare's proposal, her purse is on her right hand, but from overlooking shot it's on her left.
When Diana and Robert quarrel and he leaves the apartment they share together, a microphone is visible on the left of the scene.
The singing lady in the final scene is clearly wired up and most likely wearing a microphone under her dress.