With the Brexit process approaching its most treacherous point yet, May has summoned her senior ministers to Chequers, the prime minister’s official country residence, for an all-day summit. After months of bickering between senior ministers, May will attempt to broker a unified government position on the UK’s future economic relationship with the EU, including customs arrangements.
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Meanwhile EU leaders are bewildered that the UK is still debating matters that they rejected months ago. The overwhelming feeling in Europe’s capitals, sources in major EU governments said, is that May hasn’t yet grasped the implications of her negotiating “red lines” on leaving the single market and customs union and ending the jurisdiction of the European Court of Justice. At the same time, they contend, the EU has been firm and clear on its positions since the referendum two years ago.
Which means a deal isn't really a deal and I don't think anyone in the UK is ready for what "no deal" actually means.
...adding all this is because May triggered article 50, triggered an election, promptly lost a bunch of seats, and thus there was no workable Tory consensus. Basically it was "I'm going to point a gun at my country and shoot it in 2 years (<18 months in practical terms) if you don't give me exactly what I want but I have no idea what that is."