Today, on a full bus (214 southbound) several boys, perhaps aged 12 or
so, entered by the rear door, ordering myself who was exiting to get
out of their way and exhibiting various other obnoxiously rude
behaviours.

Not the crime of the century; not the world's biggest annoyance, but
still annoying enough. I attempted to stop them; in vain, of course,
and at the expense of more personal abuse.

I then alerted the (busy) driver, who took the information on board
and elected to ignore it and drive on, not checking the tickets of the
intruders and not taking account of those who could not get on the bus
through the correct door because of its fullness.

I can see the merit of his decision, electing to cause minimum delay
to the majority of passengers.

But other drivers might have done something else. Does LT (or whoever
it is nowadays) have policies on things like this? What are drivers
taught in training?