Originally Posted by
NickB
I have also taken the N9 multiple times to catch a very early flight without any issue. While I have not taken it at specifically the time mentioned by the OP, I have taken it (from its departure point at Aldwych or at Trafalgar Square) around 4:00/4:30am and it certainly never has been full to the point of people having to stand. I would be extremely surprised if that was the case with an earlier one, as I would have imagined that it would tend to get fuller towards the end of the night (with more people going to work) than at 3:40am.
It does get very full indeed towards the end of the night. An earlier tube service would be a godsend, but with TfL in the state it's in every time a train rolls in on schedule early in the morning it's already a miracle.