All kinds of jobs involve being vulnerable to attack by individuals, who for whatever reason, see the victims as the enemy. Teachers, doctore and nurses, social workers, police - the list goes on for ever. MPs are not alone in this. There are sensible ways of reducing risk - eg alarm buttons in interview rooms - but it can't be eliminated.

It would be good to bellieve that this tragedy could lead to a longterm change our political culture. That seems too much to hope for, but for a spell at least it might give a pause to some of the nastiness, so that it doesn't get so easily accepted.