One countermeasure which would be effective both in the protection of the
travelling public and which would also help to reduce the stress levels
among travellers would be quite a simple one; for people to talk to the
person next to them.
Travellers on London transport systems are quite famous for their reserve
and insularity; in this situation it works to our disadvantage. It leaves
individuals to suffer their stress without support or reinforcement and
slows the passing of minute pieces of intelligence across groups. In a
crisis, knowing something a fraction of a second sooner can be a matter of
vital importance.
It would also help to moderate the behaviour of those individuals who
respond to this sort of attack by indulging in racist hate.
Anyone carrying a large bag would find themselves expected to respond or
even volunteer their identity and purpose.
Failing to do so would signpost a suspect.

Talk to one another.

Steve.