Garvan Walshe was National and International Security Policy Adviser to the Conservative Party until 2008.

As in economic policy – where the Leave campaign, seeking to match the IMF, OECD, Governor of the Bank of England, and the LSE deploys Patrick Minford – so in security matters, it resorts to Sir Richard Dearlove (a former head of MI6) to argue against Eliza Mannigham Buller, John Sawers, Jonathan Evans, Baroness Neville Jones, the Secretary General of NATO, Senator John McCain and all – yes, all – our allies.

Authority is indeed stacked in favour of Remain, but you don’t have to agree with Vote Leave’s Dominic Cummings, who thinks Whitehall got everything wrong since Bismarck, to acknowledge that the conventional wisdom can sometimes err. Yet to have a conservative disposition is to think the conventional wisdom usually right, and that the burden of proof lies with those who want to overturn it.

Patrick Minford’s claims about Britain’s superior economic performance outside the EU fall apart because they rely on politically unrealistic radical deregulation. Is any British government really going get rid of banking regulation, climate change policy and maternity leave?

Far worse, not to say disreputable, is the Leave campaign’s attempt to link immigration and terrorism. Though it’s reasonable to argue that countries without border controls need much closer police and security cooperation that those that impose checks, we’re not in the EU’s border-free area: we already have border control.

In fact, the only country you can get into Britain from without having your passport checked against security databases is the Republic of Ireland. We kept this border open despite an IRA campaign that killed far more people in in the UK than Islamist terrorists have.

That is because “effective border control”, as Dearlove himself told the BBC, “is not the most important part of countering terrorism.” What matters is good intelligence and policing: and if we are to stop terrorists at the border, we need the highest level of information sharing with the countries from which the terrorists come.

Almost all the major terrorist plots that our security services are currently watching are domestic. But if we are to protect ourselves from plots hatched in continental Europe, it is with continental Europe that we must cooperate. That’s why the Government opted back in to the European Arrest Warrant and the Prüm convention on DNA sharing, and supports the European system of Passenger Name Records: those who want to leave the EU put this cooperation at risk.

In theory, this doesn’t have to be the case: we share passenger information with the United States, but in practice these European institutions are where this information sharing happens.

Here is the Leave campaign’s biggest geopolitical mistake. Because they want to conduct their business as a set of bilateral relations with other countries, they assume everyone else actually does the same. They underestimate the quantity and depth of cooperation between EU member states which is personal and political as well as institutional. Continental states play a long game because they think it’s in their long term interest to create rules by which to cooperate. If we leave, they will do everything to preserve this system, and they won’t offer better terms to the country that has left the club.

Brexiteers have been living in a bubble where they peddle myths to themselves: that £350 million leaves the UK every week – it doesn’t, because of Mrs Thatcher’s rebate; that 77 million Turks will get the same access to the EU that we currently have – they won’t, they’ll get the same access to the EU as we have to the United States; that bananas can only be sold in bunches of three – complete rubbish, as anyone can find out by visiting their local supermarket; that “we sell more to them than they sell to us” – forgetting that what matters to them is how much of their trade, not how much of ours, their exports amount to.

This leads them to overstate the EU’s weakness. It’s true that populist anti-immigrant parties across the EU are taking advantage of the migration crisis: but utterly disingenuous of the Leave campaign to argue that we must leave the EU to avoid the populism. The biggest populist anti-immigrant force here is none other than the Leave campaign itself: and if we leave the EU, it will still be here. They justify this by saying that the poor have been left behind by immigration – but it’s the working class that will be most damaged by the recession the Bank of England thinks a vote to leave could trigger.

The initial “economic shock” might be something the Leave campaign’s wealthy backers and self-hating metropolitan elite staffers can weather, but it will hit the people in whose name they are campaigning hardest.

Rejecting the advice of the intelligence agencies and our allies. Ignoring almost every piece of economic advice. Listening only to people who agree with them. And ignoring the practical consequences of leaving in favour of an imagined future. Radical? Yes. Original? Certainly. Audacious? Indeed. But in no way can it be called conservative.