In the latest incident, a car mowed down a number of pedestrians and a police officer was stabbed outside the parliament.

It was another extraordinary event on what was otherwise an ordinary day.

And we’ve seen it all before.

We’ve seen it in Berlin. We’ve seen it in Nice.

The dates change, the names change and the locations change but the sense of foreboding is the same.

It’s the sense that nothing our security agencies do will ever be enough to prevent these attacks.

It’s the sense that there will always be people on this earth whose twisted ideologies drive them them to carry out these horrors.

And it’s the sense of shock that such a terrible crime could be committed on a public street that so many of us have walked down while on holiday in London.

But these attacks also serve only to galvanise the world against its worst elements.

Prime Minister Malcolm Turnbull spoke strongly about the attacks on Thursday morning.

Around the western world, other national leaders were delivering similar messages to their people: We will not be cowed. We will not back down.

It all sounds so familiar and yet it is all so shockingly new each time – every time.

And let’s hope that’s always the case.

The sense of shock we feel when we wake to one of these terror attacks is what we need to ensure we continue the fight against evil.

We need that sense of shock to remind us that anything is possible, at any time.

We need that sense of shock to ensure we do not become complacent and to ensure those charged with protecting us do not become complacent.

Terror attacks like the one we saw in London do little to advance whatever twisted cause the perpetrator had in mind.

Instead, they bring together the rest of the world in a determination to keep fighting for what we value.

Today, Australia mourns with Great Britain for the loss of four innocent lives at the hands of a man who had lost his grip on reality.

But tomorrow we will stand with Great Britain, secure in the knowledge that most of the world stands with us.