Exactly as orchestrated, the arrival of Nathan the prophet occurs at the height of the drama. While Bathsheba is still presenting her case to King David [מצודת ציון], Nathan reaches the palace [ביאור שטיינזלץ]. Specifically, he arrives at the royal courtyard and the outer chambers [מצודת דוד, רד״ק]. He waits there for his arrival to be announced to the king, ensuring he only steps inside after receiving explicit permission [רד״ק].
Upon Nathan's entry, a distinct difference in the king's reaction is noticeable. Unlike his earlier interaction with Bathsheba, David does not ask Nathan the purpose of his visit. This difference in treatment stems from their established dynamic. The prophet was a constant presence who regularly came before the king, both day and night [אברבנאל].