The time for rhetoric, heart-felt statements of defiance and expressions of solidarity has now passed. It is not for anyone to tell you how to react emotionally to terrorism, but that reaction itself will do nothing to drive the evil back. Three times in three months the nation has rallied and shown its true grit, but the terrorists are undeterred. They cannot merely be resisted. The must be overcome.

Late last night, as the news came through that Islamists were committing murder in the shadow of the Shard – the most visible symbol of London’s potency and a place where I spent a year of my career – my second thought after the initial shock was different to what I had felt in the face of previous horrors such as this. It was not so much sadness or grief, but a cold, hard realisation that we have reached a tipping point and something stark will need to change about the entire way in which this country addresses the growing threat from the fascism in our midst.

The Prime Minister has recognised this herself, and her speech on the steps of Number 10 Downing Street this morning signalled that the sands are shifting beneath our feet. The British public will not continue to tolerate attacks of this kind. True, public opinion remains set against foreign interventions, but on the question of the intervention currently taking place on British soil, the public are united by a growing sense that we cannot go on like this.

As for the Labour Party, we have seemed unable to say anything substantive or nuanced or brave on foreign policy ever since the colossal loss of public trust that the Iraq War engendered. Jeremy Corbyn is right to say that ISIS is largely funded by Saudi Arabia, and our unsavoury dealings with the regime that rules that country are therefore partly to blame for the rise of the very death cult that struck again last night.

But you know, it is not enough to simply say we will cut off the money to Saudi Arabia. Perhaps that might form part of the solution, but stepping back from the Middle East, thereby creating an even greater political vacuum, would not solve the issue. There must be a third way, and if it involves forming new alliances, or defeating old enemies, then so be it. But we cannot simply pack up and walk away.

As to the home front, the Liberal fellow travellers inside the Labour Party would misread the public mood entirely at this crucial moment if they dared to ape the rhetoric of Tim Farron and the Lib Dems. Yes, it’s true that we cannot allow terrorists to force us to give up all our liberties, for if they ever succeeded in that endeavour, then they would have achieved 90% of their ambition. But the greatest liberty of all is the right to life, and our security and police services clearly need to be given greater powers and far greater resources to meet the growing menace.

I am sure there are those who will say this is not the time for making political points, but we cannot allow our way of life or democracy to be suspended every time we are faced with terror. For if we do, then we will have already lost. The mood of the British public is shifting, and understandably so. Our foreign and domestic policy will soon have to re-align itself, as it always does when the country is under attack.

Things are moving quickly. The course of history will move along without Labour if we allow it to. The weight of public service is a heavy burden at times like these, but Labour will lose the chance to shape British foreign policy for a generation if it does not now respond with strength and clarity.

Sam Stopp

Sam Stopp is a Labour councillor in the London Borough of Brent and is the Chair of The Labour Campaign to End Homelessness. He has written regularly for LabourList, LeftFootForward, Progress Online and Open Labour. He tweets @CllrStopp.