I had this happen on a Virgin service once. Coming down the stairs at the up end of a Pendolino at Birmingham New Street with a lot of people looking to board, and the station work complete sign was given so I hustled on in coach J (I think) along with many others. We filled the aisles in first class and there was someone further down who had just stopped dead because they didn't think there was room to move. So the train manager came along and told people to get out of the carriage or pay for first tickets, quite reasonably. I would have loved to do so, but the way was blocked, so the TM pushed past everyone, got to the start of coach H, told everyone to move down, and they all did. By one carriage. This charade repeated itself three times, and by the time I had actually reached coach E where I was supposed to be, the train had arrived at Birmingham International which was as far as I was going!