On a GWR Class 800 that I was on in First Class last weekend, many people got on in in the First Class carriage, and then just stayed put. Although maybe that had something to do with them having reservations in this carriage. The guard didn't hesitate on throwing them out though, wondering if that's even allowed but okay...
If they did not have 1st class tickets how could they have reservations in the carriage?
Following this event I experienced last Sunday, I am left wondering what passenger rights are, should they have a reservation in a first class seat with a standard class ticket.