I am bewildered by the perverse attitude being expressed in this thread that the railway industry should not take reasonable steps to reduce fare evasion and fraud; in particular, the idea that insisting on proof of status before selling tickets at a discount is somehow reprehensible. We have several threads in this forum about fare evasion with detailed first hand evidence of the kind of tricks that a rogue element gets up to. The railway today is in a period of financial crisis which threatens its future existence. This is exactly the right moment to crack down on fraud and if doing so drives away that rogue element, so much the better. Honest people do not object to being asked to prove their status and it's delusional to imagine they would shun the railway forever more if asked to do so.
I live in London and, because of my age, I have a Freedom Pass. That does not entitle me to turn up at a station without my pass and breezily declare "I'm entitled, I'm entitled" and just catch a train. I have to bring my Freedom Pass with me and if I don't, I can't travel. Being obliged to carry evidence is no imposition at all and I'm astonished that some posters think it is.
I’d agree with this. Similarly I’m expected to show a priv card when buying a priv ticket - it’s no great hardship and I’d fully expect to be refused service or sold a full price ticket if I couldn’t produce it.