Note 1 at Lu 22:59: Peter's three denials of our Lord took place in the palace of the high priest during the religious trial of Jesus (Mt 26:69, Mr 14:66, and Joh 18:15-16). Three out of the four Gospel writers grouped the denials together for the purpose of clarity (see note 1 at Lu 22:54), but it is clear that they did not occur in rapid succession. This verse even states that it was about an hour's time between Peter's second and third denials.

Note 2 at Lu 22:59: This is the culmination of Peter's denial. There were actually three steps in Peter denying the Lord. First, as mentioned in note 6 at Mr 14:37, Peter's denial actually began with his failure to pray with Jesus in the garden. Next, Peter followed Jesus "afar off" (Mt 26:58, Mr 14:54, and Lu 22:54). Last, Peter started keeping company with the wrong crowd (see note 4 at Joh 18:18). Sin has to be conceived. It doesn't just "happen" (see note 7 at Mr 14:38).