There is no more road. This week the can hits the wall. Theresa May must present her Brussels negotiators with an agreed cabinet template for Brexit, or they, and she, will slither into chaos. She must end the intransigence of her rebel cabinet members, who must accept her leadership or go. The public interest requires that this week be Boris Johnson’s last as foreign secretary.

May’s negotiators under Oliver Robbins will on Friday present the cabinet with what was always the only sane option for a post-Brexit Britain – a version of the Norwegian model, of a single market within the framework of the old European free trade area, now called the European Economic Area (EEA). The nation’s economy is too integrated with Europe to go back to walls and barriers.

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There was an argument for Britain leaving the EU, a cartelised, inflexible, over-centralised group of states now showing every sign of traumatised decay. There was never an argument for Britain disintegrating Europe’s economic space. Pretending Britain could sensibly replace this by “trading freely with the rest of the world” is nothing more than post-imperial romanticism.

All recent polls show that the electoral driver behind Brexit was curbs on migrants from outside the EU, and on benefits for those from within it. Such curbs are now the common currency of European politics and are being negotiated on all sides. And the EU’s trading partners are not its “vassal states”. All countries that trade with other countries must accept their conditions and agree courts of arbitration. Voter concerns on such details can be met.

Where Robbins’ paper appears to leave no doubt is that the Norway/EEA option is the only one on that Brussels will negotiate. It is under no pressure to consider anything else. No other template – short of fortress Britain (and Ireland) – can be envisaged. Robbins’ one concession to the critics is that open borders will apply to goods not services. But the EU has little of a free market in services, with matters such as finance and professional certification handled ad hoc. More to the point, the Robbins plan is coherent and would have the support of the country and parliament as a whole.

Now enter the leadership. For 18 months there has been no agreed Brexit plan because of Britain’s feuding cabinet. That feud has had nothing to do with the national interest, only with Tory leadership disease. That disease, the cult of disloyalty, has cursed the party with six leaders in two decades. Its arch carrier, Jacob Rees-Mogg, today warns May of the fate of Robert Peel over the corn laws. He commits history abuse. He should rather recall how Margaret Thatcher fared when her leadership was similarly undermined in 1981. She dealt ruthlessly with her enemies, and won.

• Simon Jenkins is a Guardian columnist