The complicated etiquette of the empty train seat

The empty train seat looked inviting, and all three of us stared at it, then looked away, not daring to either take it, or offer it to the other. This train from Clapham Junction to Surrey was absolutely packed. But when someone got up and there was a seat right next to me, I realised that under the prevailing conventions relating to equality, I could neither take it nor offer it.

I was squeezed between two ladies, one quite elderly who looked exhausted and desperate for a seat. She was standing slightly behind me, so, technically speaking, I was in line for the seat. But as she clearly had a good 20 years on me and looked tired, she should have the seat, the way I was brought up.

As I looked to the newly available seat, and back to her, she very purposefully looked away and refused to meet my eye, which I took as a possible sign that if I did offer her the seat, she would feel I was insulting her and being ageist.