In the seven months since the UK triggered Article 50, not one week has passed without the cabinet's Brexit divisions being openly exposed. This week it was David Davis suggesting that MPs may not get a vote on the deal before Britain leaves, and Boris Johnson unilaterally guaranteeing EU citizens the right to remain.

After Theresa May contradicted Davis at PMQs, the Brexit Secretary's own department stated that he "expects and intends" that an agreement will be reached in time. Johnson, meanwhile, told a meeting of the Belvedere Forum on Polish-UK relations: "We have 30,000 businesses in this country that are Polish. We have one million Poles in Britain. We are thoroughly blessed, we are lucky. And I have only one message for you all tonight: you are loved, you are welcome, your rights will be protected whatever happens. Yes. You are recording this? Your rights will be protected whatever happens." A few hours earlier, Johnson told MPs that a deal had not been reached and that it was “up to our friends and partners in the EU now to look seriously at the offer we are making and, particularly on citizens, to make progress". So not only are cabinet ministers disagreeing with each other - they are now disagreeing with themselves.

For EU negotiators, such divisions are a gift. Faced with contradictory messages from the British government, they have every excuse to delay progressing the talks. But Brussels' professed bafflement is not merely tactical. They see Home Secretary Amber Rudd declare that a "no-deal" Brexit is "unthinkable" and Davis insist that "we need to prepare for all the other alternatives". They see Liam Fox argue that the UK could trade comfortably on WTO terms and Philip Hammond dismiss this possibility. And they see a Prime Minister too weak to unite her cabinet. For fear of provoking unmanageable divisions, Theresa May has delayed talks with her top team on the UK's new trading relationship until next year.

Brexit is the greatest challenge any British government has faced since 1945. The divorce rules are purposely designed to favour the EU. Any deal must be approved by at least 72 per cent of member states, representing 65 per cent of the EU’s population. The two-year deadline for leaving can only be extended by unanimous agreement.

For these reasons, the UK was reckless to trigger Article 50 as early as it did. As Britain's former EU ambassador Ivan Rogers told the Treasury select committee earlier this week: "My advice as a European negotiator was that that was a moment of key leverage and, if you wanted to avoid being screwed on the negotiations in terms of the sequencing, you had to negotiate with the key European leaders and the key people at the top of the institutions and say: ‘I will invoke Article 50 but only under circumstances where I know exactly how it is going to operate.'"

Leave supporters have routinely accused individuals and institutions – the Bank of England governor, Mark Carney; Philip Hammond; the BBC; the civil service – of undermining and even "sabotaging" Brexit. But the truth is that, too often, the Brexiteers have undermined themselves.