In the nearly 20 years I have served in parliament, Westminster has seldom been more fractious or bad-tempered. It is a place of many speculative – but totally inconclusive – elevator conversations about what will happen next, and of developing despair among sensible figures in both the two big parties.

One of the nonsenses that they are dealing with is the prospect of a no-deal Brexit. The government is trying to scare people into believing it could happen by accident, and they’re spending £4bn of taxpayers’ money on faux “preparations”. Arch Brexiteers, meanwhile, sell it as a virtue: “Why don’t we just walk away?” A simple solution to a very complex problem with a measure of defiance thrown in, putting up two fingers to the bullying, interfering Europeans.

Yet for the government to keep open the prospect of there being no deal is a cynical form of psychological warfare, designed to frighten people into supporting her. The original rationale was that the possibility of no deal strengthened the government’s negotiating position with the EU – ministers could ostensibly flounce out of the talks. But now an agreement has been reached with the EU that rationale has disappeared. And pretending that no deal can come about inadvertently is just a deception. If it was to happen it would be a deliberate choice of the British government. The government could stop it by the simple device of seeking an extension of Article 50 or cancelling it, as the European Court of Justice has ruled it can.

As with all things Brexit, no deal is not actually a concrete proposition. A “managed no deal” is mooted, which presumably means that agreement (a limited form of “deal”, then) is reached with the EU to prevent a complete breakdown in contractual relationships: permitting aircraft to fly and channel ferries to operate.

The proponents of this route arrogantly assume that the EU would be only too willing to agree. And some Brexiteers are also advocating that the UK should – in this process – simply default on its contractual financial obligations to the EU, following the model of Argentina and Venezuela. The traditional demands of the populist left on the lips of the traditional right. The mind boggles.

But the key step is to accept that there is no transitional agreement for trade and that at the end of March Britain reverts to WTO (World Trade Organisation) terms. The phrase, WTO terms, sounds reassuringly bland and authoritative but, in reality, is nothing of the kind. The WTO (formerly GATT) is an organisation I, as a free trader, strongly believe in, in much the same way as I believe in the United Nations. Its free trading, principles and the commitment to non-discrimination is admirable. But in practice, the only countries which trade purely on WTO terms are those with one foot inside the global capitalist system and one foot out (China, Russia, Venezuela). This is not a model for modern Britain to follow.

There is little or no coverage of services – financial, creative, digital – which are the backbone of the British economy. There is no commitment to common technical, safety and consumer standards in goods, which presently underpin so much of our trade and particularly the complex supply chains which sustain many manufacturing industries. And the tariffs involved are potentially lethal for exports of foodstuffs like mutton, leading to a sharp fall in prices and the need for large scale slaughter to support the market (as happened in the foot and mouth epidemic).

Worst of all, no deal involves walking away from the Good Friday Agreement: a course of action that could devastate a fragile peace on the island of Ireland.

It is therefore time that a no deal was taken off the table as a serious option. The only plausible choice now is between Brexit as made real through Theresa May’s wholly unsatisfactory agreement or staying inside the EU.

The strength and solidarity Europe has demonstrated over two years of negotiation demonstrates all too well why we should continue to play our full part. Liberal Democrats have now argued for two years that the eventual deal should be put to the people for a public vote. That prospect is now real, but first the chimera of no deal must be put to bed.