Offering One's Seat
In the past it was always considered courteous for a man to
offer his seat to a woman. It is now a more tricky matter of
There is no need to jump up on the train or underground every time you see a woman standing (unless she is definitely pregnant or elderly, when it is a definite requirement).
But if circumstances are particularly taxing or uncomfortable, and you're feeling chivalrous, you should offer - she can always refuse.