The recent 448-75 parliamentary majority in favour of Theresa May triggering article 50 (A50) by end March, just weeks away, probably marks the final defeat of those of us who continue to believe that Brexit will be an unmitigated disaster for Britain. Continuing the argument may now be pointless. Before I bow to the puerile demands of the Brexiteers to “respect the will of the people” and “get used to it”, here are five valedictory reminders of the mess we’re in.

An A50 trigger is irrevocable and must be unconditional. That is the government’s considered, self-harming legal opinion in its statement of the government case to the Supreme Court. Largely unnoticed, it has massive implications. Even if the agreement negotiated after the trigger is so damaging to Britain that it’s rejected by parliament, or in a referendum on its terms, we shall still be out of the EU two years later, either with an unacceptably harsh agreement or – worse still – with no agreement at all. Once A50 is triggered, there is no going back.

The referendum last June was a snapshot of the opinions of those who voted then, in the then limited state of knowledge about the true implications of Brexit. If parliament had intended it to be a “decision” binding on government, it would have said so in the referendum Act. It was “advisory”: it counted the opinions of those who opted to vote on a specific date. Its only message was that the opinions of voters on that day were almost evenly divided. The 52 per cent voting to Leave represented neither a majority of the adult population nor “the will of the British people”. This was never a credible basis for overturning decades of British policy, law, global status, trade advantage and cultural identity.

Since the referendum, a huge amount of new information has emerged, both about the complexity of unravelling decades of law-making, agreements, obligations and privileges dependent on EU membership, and about the deeply unfavourable terms of our exit that are plainly going to be imposed on us by the EU27 (the rest of the EU), to deter others from trying to leave and to penalise us for leaving – and for our relentlessly negative and uncooperative behaviour in the EU in recent years. As this reality gradually sinks in, it will be extraordinary if at least 3 or 4 per cent of the Brexit voters don’t start to re-think their positions, and to regret their referendum votes – which will make the Remainers a majority. But if A50 has been triggered by the time that happens, it will be too late.

It’s obvious madness to throw away all the trade and other advantages we enjoy as an EU member purely in order to gain the legal right to reduce immigration from the EU. Migrants from the EUare always fewer than half of all immigrants. We have always been completely free to reduce most immigration, that from outside the EU, if we wish. We have totally failed to reduce it in the face of the reality that we need the migrants for their contribution to the growth of our economy, the jobs they create, the scarce skills they provide and their willingness to do jobs that native Britons spurn. We can’t reduce non-EU immigration despite having every legal right to do so: why should we be able to reduce EU immigration if and when we secure the legal right to do so, at the colossal economic, trade, political, diplomatic, security and cultural cost of leaving the EU?

The absolute duty of members of parliament, including peers, is to act and vote in accordance with their own best judgement of the best interests of our country. Most of them know that Brexit on even the most improbably favourable terms will damage Britain far more than remaining in the EU and tackling the grievances that led many Brexiteers to vote to leave. Such parliamentarians can’t reconcile that duty with voting for a A50 trigger by the end of March. They might possibly be excused for supporting a compromise: not triggering until after next year’s French and German elections, i.e. after mid-May, when we can make a meaningful assessment of the terms likely to be imposed on us by the then leaders of the EU27, and indeed of the EU’s chances of survival, before we burn our boats.

Future historians won’t understand how almost all our parliamentarians, a majority of whom know that Brexit spells ruin, followed a weak and confused government in choosing to interpret a snapshot of partial opinion, half a year ago, as a binding instruction to commit irrevocable national suicide. Are Ken Clarke, Caroline Lucas, the LibDems, a few Labour rebels and the SNP the only honest politicians we can count on to do their duty and oppose Brexit by every possible means?

On Brexit, the argument is over: unless the government loses in the Supreme Court, giving parliament one last opportunity, before the end of March, to stave off disaster.