FOR months, as the clock has ticked towards a two-year deadline for Britain to leave the European Union in March 2019, Theresa May’s government has been criticised for being ill-prepared, divided and unrealistic in its approach to Brexit. And rightly so. However, this week it took a belated step towards reality in the first two of a series of Brexit papers, on future customs arrangements and on Northern Ireland. It accepted explicitly, for the first time, that a temporary transition, or interim period, will be necessary to avert a damaging cliff-edge exit in March 2019, and that in this interim period Britain should be in a customs union with the EU.

That is a big step forward. It is all the more surprising, because it came just days after Philip Hammond, the chancellor, and Liam Fox, the trade secretary, promised in a newspaper article that, even in an interim period, Britain would be out of the EU’s single market and customs union. The official Brexit paper acknowledges that this may happen eventually, and offers ideas for a new customs regime that, although burdensome and quite possibly impractical, at least tries to minimise the costs to traders (see article). But in the meantime the paper proposes an interim temporary customs union that will be tantamount to staying in the current one. Dr Fox insists that, as is not the case today, he will be able to negotiate free-trade deals with third countries while Britain is in this interim customs union. He is wrong. No trade deal can take effect so long as Britain is in a customs union. And no country will be willing to negotiate the details of any deal until Britain’s own future trade arrangements with the EU are clear.

A transitional period with a temporary customs union will put off the problem of how to keep the border between Northern Ireland and the Republic as frictionless as possible. But once Britain leaves the customs union, border controls in some form will surely be necessary. This will damage the island’s economy and destabilise its politics; the Irish government is rightly unhappy. Although the British government’s paper persists in the vain search for a technological solution that can magically avoid any border at all, it does at least acknowledge that Brexit will involve significant administrative costs for both parts of the island.

Those trade-offs

The government now needs to build on this new, more sober approach. Detail and realism should be the hallmarks of the big Brexit speech that Mrs May plans to give next month. One part of this must be to concede that Britain is bound to face a substantial exit bill, for without this the EU will not be prepared even to talk about trade. And when it comes to these talks, Mrs May must be more open about the compromises they involve. Put crudely, the more control Britain takes back from Brussels, the bigger will be the hit to its trade and thus to Britons’ living standards.

Mrs May also needs to accept that other countries also have politics. Too much of the Brexit debate in London has been internally focused: resolving cabinet disputes, trying to keep Parliament onside, working out what the Labour opposition really wants. In the end, however, the trickiest negotiations will be with the EU 27. Securing the necessary majority in Brussels for an exit deal will be hard enough. But when it comes to transition or, even more crucially, to the ultimate trade arrangements, the other countries must agree unanimously and their parliaments must ratify the deal. That will take time, probably years, and it will need defter diplomacy than Mrs May’s government has displayed so far. This week’s papers are but a first step towards a more realistic approach to Brexit.