Sometimes when my train is super busy - either cause of previous trains being cancelled, or it being lopped off onto a 4-carriage rather than 8, they "declassify first class" which, as someone with a standard ticket, is great. But if I were actually a first class ticket holder, I'd be utterly fuming. That's exactly when I'd want it enforced. I mean, it's not like Virgin where you actually, like, get something for first class. The seats are barely even bigger, and they're equally covered in piss. Literally the only difference is that you're far more likely to actually get a seat. So if they just said "Well, it's busy, fuck it", I'd be cross. Very cross.