Serious question for you given your background.
You see this happening on the tube and some old pensioner (right or wrong) getting battered.
Do you intervene?
I don't care if the old guy did wrong but you just don't go beating up an old senile man in my opinion.
I would have been very tempted to teach the young fella a lesson there.
id have stopped the young kid after the second dig
they were about quits then
the old guy shouldn't get away scot free
funny thing is if the old guy was a chick everyone would have piled in to defend her even if she started it
ive intervened in some quite tricky shit ive been lucky that its never gone south on me