If the EU referendum taught this country’s pro-Europeans anything, it ought to be that they lacked the political focus and discipline of the leavers. Pro-EU campaign complacency proved no match for pro-Brexit fanaticism, with catastrophic results. Something similar is now in danger of happening again, as the Brexit process reaches a critical milestone: the end of phase one of the Brexit talks. If Britain is not to pitch out of the EU without a deal, it is vital that history does not repeat itself. But the danger of that is very great.

The trigger for the current crisis was the Democratic Unionists’ derailing of the draft EU-UK phase one deal in Brussels on Monday. That happened because of an inexcusable political oversight. The UK government did not share the content in advance with its DUP backers, who pulled the plug, fearing that Northern Ireland would be put into a special status separate from the rest of the UK.

Since Monday, however, it has become much clearer that the UK government’s failures and incompetence on Brexit go wider and deeper. Philip Hammond confirmed on Wednesday what this column had reported, that the cabinet has never at any time had a specific discussion about the kind of Brexit that it is aiming for. As Sir Keir Starmer said in a Guardian article, membership of the single market, the customs union and a role for the European court of justice were simply swept off the table as options by Theresa May’s grossly irresponsible diktat of October 2016.

David Davis’s revelations at the Brexit select committee on Wednesday compounded that lack of direction with further shocking admissions. Amid clouds of characteristic bluster and solipsistic swagger, it eventually became clear that Mr Davis has at no point set about an assessment of the consequences of Brexit for the British economy and for UK jobs and conditions. The “impact assessments” for 58 UK economic sectors that parliament had demanded in order to better understand the Brexit options turned out not to exist at all. The only rational explanation for this extraordinary neglect of public duty and misleading of MPs is that Mr Davis knows such impact assessments would paint a bleak picture wholly at odds with the vacuous optimism of the Brexiters.

The document that Mrs May had intended to sign on Monday before the DUP vetoed it is a practical one as far as it goes. The thread running through it is the UK government’s quiet willingness to compromise on the key issues – rights, money and Ireland – set out in Michel Barnier’s April 2017 brief, presumably in the over-optimistic hope that this will help secure a beneficial trade deal with the EU in phase two. Yet when Mrs May was challenged on her Brexit strategy at prime minister’s questions on Wednesday, she gave none of the leadership that is now needed in defence of compromise, convergence, alignment and the economic security that she should have invoked. Instead she reiterated the deluded and contradictory mantra that has got Britain into this mess in the first place – leave the single market and customs union, no hard border and a close partnership.

This proved enough to see off a disappointingly ineffective, though welcome, set of criticisms of her Brexit handling by Jeremy Corbyn at PMQs. But it cut no ice at all with either the DUP, who are in their element as the tail wagging the Tory dog, or with the Tory party’s Brexit obsessives. Following Iain Duncan Smith’s lead on Tuesday night, in which, completely irrationally, the former party leader accused the EU not the UK of causing the talks breakdown, three hardline Brexit MPs rattled their swords behind Mrs May with insistences that no red lines must be crossed. It is clear that the fanatics scent blood. They see an opening to ensure the talks collapse next week with the no-deal outcome that they crave as the prelude to their desired bonfire of the social regulations.

The crucial question in politics is therefore whether the pro-Europeans have the weapons and organisation to stop this. In an important intervention this week, Nick Clegg made clear that the leave fundamentalists are focused on reaching March 2019 with the minimum of pledges to regulation or convergence. Those who oppose this scorched-earth Brexit must now match them, steel for steel, working as one, as Mr Clegg argued. That approach requires significant amendments to the withdrawal bill and parliamentary votes that put the national interest ahead of party. As so often, for the bad people to triumph it requires merely that their opponents do nothing effective. That happened in the referendum campaign. It absolutely must not happen again now.