E VEN AS THE House of Commons began five days of debate on Theresa May’s Brexit deal this week, MP s were focusing on the vote due on January 15th. Everyone (except perhaps the prime minister herself) expects it to be lost. But nobody agrees on what happens next. Mrs May has simply warned MP s that they will be entering “uncharted territory”.

This is not for lack of alternative plans. They range from a Canadian-style free-trade deal, through a Norway-like option, to a second referendum. But at present there seems to be no majority in Parliament for any of these. And there is another inconvenient truth. According to both British law and Article 50 of the European Union treaty, Brexit will happen on March 29th, deal or no deal. Hence the government’s ramping up of no-deal planning, which has included such comically inept events as the award of a contract for ferry services to a firm that has no ships.

The real purpose of such exercises is not to prepare for a no-deal Brexit, for which it is now far too late. It is to intimidate wavering Tory MP s into backing Mrs May’s deal. So far this does not seem to be working, partly because hardline Brexiteers, like most Tory party members, favour what they like to call a “managed” no deal. Yet as became clear in voting on the finance bill this week, a majority of MP s, including dozens of Tories, are vehemently against a no-deal Brexit.

Despite this, such an outcome is surprisingly hard to stop. It is now, in effect, the default option. As Cathy Haddon of the Institute for Government, a think-tank, puts it, “Parliament can vote for any number of motions, resolutions and amendments to bills, but none of these on their own is enough to stop no deal.” Only three things, she says, can do that: passing an agreed Brexit deal; seeking an extension of Article 50, which needs the unanimous approval of 27 other EU governments, some of which will be reluctant; or revoking the original Article 50 letter, which can be done unilaterally up to March 29th but would be hugely embarrassing for Mrs May.

A cross-party group of MP s is now trying out a variety of ways to force the government to take a no-deal Brexit off the table. As it has done many times recently, the government can ignore votes in Parliament, even if they have some political force. But on January 8th Yvette Cooper, a Labour MP , successfully pushed through an amendment to the finance bill to make it unlawful for the government to vary taxes following a no-deal Brexit without explicit parliamentary approval. This may well presage further rounds of guerrilla warfare by MP s.

There are plenty of potential targets. At least nine Brexit-related bills need to be passed before March 29th, including on such matters as trade, immigration and agriculture. Any of these could be amended to make a no-deal Brexit harder. Some MP s have also suggested that they might vote to cut ministerial salaries. Several Tory backbenchers and even some ministers have threatened to resign their party whip to fight against no deal. In extremis they could join Labour in voting the government out of office and triggering a general election. But, as Ms Haddon points out, even this would not on its own prevent a no-deal Brexit.