One of Theresa May’s main reasons for pushing the customs partnership idea is that she believes that there’s a majority in the Commons for a customs union.  First square the Soft Brexiteers there, the logic runs.  Then go back to the EU with the customs partnership idea.  In the meanwhile, the harder Brexiteers won’t dare bring the Prime Minister down.  This is a) because they won’t want to take the blame for deposing her and b) a new leader wouldn’t change the Commons arithmetic – no matter how pro-Brexit he or she might happen to be.

But is this calculation right? Caroline Flint wrote in yesterday’s Sunday Telegraph that “Parliament should reject Brexit game-playing and accept the country’s decision” – as the headline on her piece puts it.  Flint is the perfect illustration of a former Remainer whose working-class seat voted emphatically for Leave: 68.5 per cent of her constituents in Don Valley did do.  Some argue that the customs options are too arcane to make an impact in such seats, especially since the defenestration of UKIP.

We cannot be sure.  Amidst the modern-day febrile politics of Trump and Orban and the AfD – even Macron is a bringer of revolutionary political change – the claim that the referendum result has been betrayed could be a potent one.  Flint and Labour MPs like her in the midlands and north will be very nervous.  Have the Conservative whips made any assessment of potential Labour rebel support, were May to rule out the customs partnership?  If not, why not? Is Downing Street taken an interest?