We always knew, if we had any sense, that this was coming. Outrages in France, Belgium and Germany last year were uncomfortably close to home, though at least they were on the other side of the Channel. But Britain has always been just as much of a target for terror, and it's only the skill of our intelligence services that has kept us safe so far.

Now that illusion of invulnerability, if it existed, has been shattered. We do not know for certain at the moment who's behind this horror. But that it's some kind of terror attack at the heart of our democracy appears certain.

It's very tempting, when such things happen, to look immediately at the big picture. This is Westminster, the Mother of Parliaments. It has a huge symbolic value. Whoever did this could hardly have struck at a more significant target.

All this is true. But the immediate aftermath is much more personal. Westminster is a workplace like any other. People turn up expecting to do their jobs, go home and get paid. You can't be around Westminster without noticing the security presence there, but you become used to it – you never expect it to matter. Now, though, it does. Inside the Palace there are people who are shaken by what's happened, who might know the victims personally, who have suddenly had their foundations kicked out from under them. Outside there are people walking by, or across Westminster Bridge, who know it could have been them. 

People have died and been seriously injured. The terrible, life-changing grief that these moments of wicked madness have brought to whole families is dreadful to think of.

So as we think of the big picture, let's think of the small ones too, and pray for Westminster: the individuals who've been traumatised and bereaved, and those whose world has been shaken and who will go home trembling at what they have escaped. They are not just politicians, administrators and bystanders, they are people. May God comfort and console them.