I regularly go between Manchester and Leeds, which is nearly always jammed, even at off-peak. Thus I usually book a seat, as I'm usually carrying luggage and the idea of standing with a suitcase in the vestibule for an hour doesn't fill me with great joy. My policy regarding elderley people is that I look at them to see if they need the seat, and if they do, I will offer it. What I won't do is offer it to someone who assumes that just because they are "old" they "deserve" the seat more than me. I'll list three scenarios, each with different outcomes -
1. Get on at Leeds, 17.40 train to Manchester on Friday. Rammed obviously, but had reservation in Coach B. Woman in mid 60s comes along, carrying tonnes of shopping bags, I let her on in front of me, being polite. She moves down the carriage, sees my reserved seat empty (miracle!), looks at it, and decides to sit down. I'm behind her, and say politely, excuse me, I've reserved that seat. Reply: "I'm elderley, I need it, you can stand". I refuse that justification, and threaten to get the guard. She moves reluctantly, denouncing all youth. I think I made a reasonable call - she clearly wasn't in need of it, being able to carry 4 large shopping bags, and she saw the reservation, and decided to ignore it, simply because she felt she had a "right" to it as an OAP.
2. Sat down on train from Manchester, arrive Huddersfield 8.30am Monday AM - obviously tonnes get on there. Again, "fit" elderley person in early 70s gets on, and as she fancies a table seat, asks me to move in a very "One Foot in the Grave" style manner - pretty much, oi boy, move, I want to sit there. Taking offence at her tone, I refuse to move. She ends up standing - the Hudds commuters clearly thought her attitude was out of line too.
3. Get on train at Leeds, sit in reserved seat. Person in 70s asks to sit down, asks politely, and has a walking stick. Obviously, I let her sit down as she clearly needs it, and has the common decency to ask in a nice way.
Conclusion - OAPS have no "right" to a seat unless they reserve one, but if they ask in a nice way, I'll give it up. However, if they assume they have a right to the seat, and are rude, then they wont get it. Simple human decency at play.