Nick Herbert is a former Minister for Policing and Criminal Justice, and is MP for Arundel.

With Christmas arrives the inevitable repeat of It’s A Wonderful Life, in which an angel dissuades James Stewart from committing suicide by showing what the world would have been like without him. Come down, heavenly bodies, and reveal to my fellow Conservative MPs the future they could so easily enjoy but seem about to jeopardise.

In Christmases ahead, we could be out of the EU, the Common Fisheries and the Common Agricultural policies. We could have a free trade deal with the EU and with other countries around the world. We could have control over our borders. No more eye-watering sums would go to Brussels. Our Parliament would be back in control. These gifts are now within sight. But we have become hung up on legalistic objections to the divorce agreement which are out of all proportion to the political gain of a new relationship.

The kernel of the case against the Withdrawal Agreement is that a backstop could lock us into a customs union with the EU forever, preventing us from doing trade deals and subjecting us to EU law. We are told that the EU would trap us forever in this limbo rather than offer a decent trade deal. Brexiteers used to assure us that the EU would be bound to do a good trade deal because “they need us more than we need them”. Still, concern about the backstop must be taken seriously, not least because it has now become the hook on which so many Conservatives have impaled themselves.

The UK agreed a backstop last year. It’s an insurance policy to ensure no hard border between the Republic of Ireland and Northern Ireland in the event that a free trade deal with the EU isn’t completed by the end of 2020. Almost everyone agrees that such a border must be prevented. However the backstop would no longer keep Northern Ireland alone in a customs union with the EU, because the Prime Minister successfully insisted that it would encompass the whole of the UK. It’s a far more acceptable measure than it was before.

But the key point about the backstop is that we want to avoid it, and that even if we can’t it could only be a temporary state. We could extend the transition period for a short time instead. We could develop technological alternatives to a hard border, a solution that Brexiteers tell us will be straightforward. The backstop could not be permanent because, legally, it can only be a step towards a trade deal with the EU. There is a mechanism by which we could get out of it against the EU’s will, albeit an imperfect one. And while Ministers can never say that the UK would breach a Treaty obligation, if we really did become snared, what could stop our sovereign Parliament from just getting out?

But these are all the darkest of scenarios. Despite Emmanuel Macron’s posturing, the EU doesn’t really want us to get into a backstop, either, ironically because they believe that it will unfairly advantage us. What we all want, and can have, is exit followed by a free trade deal. So let’s stop describing temporary measures as though they were the end state. They’re not. Let’s stop fuelling outrage with overblown warnings that Britain will become a “vassal state” or – even more absurdly – a “colony”. And let’s stop fetishising betrayal. Every time a Conservative MP unwisely – and wrongly – says we’re failing to honour our manifesto or our promises they give a hostage to fortune and profit opponents who tell voters we can’t be trusted.

In becoming so obsessed with the backstop we have lost sight of the prize. The Political Declaration agreed by the EU proposes a free trade deal that could look remarkably like the ‘Canada plus’ model that Brexiteers have been espousing. There’s no mention of Chequers. The declaration promises a close economic partnership with the EU, yet gives an explicit commitment to ensure we can strike trade deals around the world. What every Conservative should be doing is calmly weighing up the pros and cons of the divorce arrangements and the future relationship in the round. Instead, too many MPs have rushed to public judgement on one aspect of the Withdrawal Agreement without thinking through the consequences.

Those of my fellow Tory MPs who are proposing to vote against the Prime Minister should pause to consider why they will find themselves in the same lobby as Jeremy Corbyn or MPs who want to stop Brexit altogether. No-one knows the consequence of voting down the deal, but it’s unlikely to be a harder Brexit when the substantial majority of MPs want precisely the opposite. In insisting on ideological purity, obsessing over the legal trees while failing to see the political wood, Conservative MPs may fell their only chance to secure the kind of Brexit they want. If they really think a free trade agreement with the EU will render us a “slave state”, they should try a Norway-style membership of the EEA plus customs union for size. Good luck as they attempt to explain why the public can’t have full immigration controls, we won’t be able to strike global trade deals and we’ll still have to pay billions into a European budget.

In the worst scenario following rejection of a deal, there would be an election. In another, the Commons could fall back on a second referendum. No-one can say what the question could be, or explain why we should honour a second referendum if we dishonour the first. Few appear to have thought through the consequences of an even narrower margin of victory for one side, deepening the wounds of division in the country rather than healing them. The euphemistic “people’s vote” is in reality the politicians’ device, an excuse dressed up as direct democracy to renege on a decision already made and a promise faithfully given. So far, it deservedly hasn’t commanded majority parliamentary support. But watch Labour MPs who long to ditch Brexit inch towards it.

The Meaningful Vote on 11 December will present Conservative MPs with a stark choice: delivering an orderly and pragmatic withdrawal, followed by the free trade deal with Europe that Brexiteers wanted, or a plunge into unknown territory that is most likely to result in Brexit delayed, diluted, or even ditched altogether. We have the prospect of an economic bounce and a dividend for public services and tax cuts, or further uncertainty for business and a risk to jobs. We could provide a smooth transition to reassure investors, or risk no-deal chaos of the kind which can destroy a government’s reputation for competence for decades. The hardliners will never accept that the Brexit glass is way more than half full, and that overall the offer is good, not least because many of them really want no deal. But usually-pragmatic Tory MPs should think hard before joining them and taking such an unnecessary gamble.

Another Christmas movie perennial, Bridge on the River Kwai, reappeared last weekend. “What have I done?”, gasps Alec Guinness, as at last he realises his folly, staggers over the detonator and blows the bridge he misguidedly built for his enemies. There’s still time for Conservative MPs to recognise, in the final words of the film, the “madness, madness” of siding against the very thing for which they have yearned for so long.