Backstop meant that the Withdrawal Agreement had to fail

But it was also necessary, and it all goes back to the Irish backstop.

Thirteen months ago, in December 2017, the prime minister made a foolish commitment on the Irish border: not merely a pledge that there would be no hard frontier on the island, but in effect that there would be no customs or regulatory divergence.

It took a long time for the consequences of this to become clear, but in recent months they did: a border would arise in the Irish Sea to placate Dublin’s demands on the land border.

The Withdrawal Agreement that last night was so heavily rejected by Parliament represented an almost complete climbdown by Theresa May on what she had said would be her red lines. Initially, the prime minister’s oft repeated maxim, Brexit means Brexit, was backed up by her insistence that the UK would leave the customs union and single market.

She agreed over the Irish Sea something that she said no prime minister could ever agree. Bizarrely, business in Northern Ireland backed a deal that would have meant an immediate regulatory border in the Irish Sea and possibly a customs one too if Great Britain had ultimately left the customs union. Few business leaders have outlined why they think barriers to NI’s most important trade, that with the rest of the UK, was a harmless prospect.

But while defeat of the deal by a huge margin is appropriate, and an outcome that underlines the risk Ireland has taken in being so wedded to the backstop, the situation is not a happy one. The DUP is right to support the government in tonight’s confidence motion, but there are many perils ahead. It might be that the Conservatives offer Labour a customs union to avoid ‘no deal’, which will be a fresh development that could make Brexit seem pointless and will cause disillusionment in many of the 17 million people who voted for it.