FOR present needs, a cartographer drawing up a map has to ensure that it corresponds to the contours of the landscape. This applies as much to figurative road maps as to geographical ones. For the future, conveniently, map-makers can produce whatever they like and insist that the landscape will comply. This was apparent on Tuesday in the Prime Minister’s remarks on Brexit, recounted as if the European Union states would have no say in the matter. For example, she will push for a new “comprehensive free-trade agreement” that would give the UK “the greatest possible access” to the single market. There was no need to use a crystal ball: such agreements exist already. But, in the inconvenient present, non-EU countries such as Norway must adhere to EU regulations to trade with the single market. No wonder Mrs May declined to make the comparison. Similarly with the EU customs union, which lifts tariffs on goods within the EU, Mrs May spoke of her plan “to have a customs union agreement with the EU”. A future agreement can contain all the qualifications one wishes and none that one dislikes. It will become reality, however, only when the EU leaders have had their say. The result is unlikely to be congenial.

As for the impression given that a “free” Britain will attract more trade from elsewhere in the world, this is likely to come about only as a result of a devalued currency, something that President Trump affirmed cheerily earlier in the week. But trade with the EU remains critical to the UK’s economic future, amounting to roughly half its trade (in the latest figures, for November 2016, 48 per cent of exports and 54 per cent of imports). Any disruption would be harmful.

The problem with the vote in Parliament, accepted as legally necessary in Mrs May’s speech on Tuesday, is that it must take place before the triggering of Article 50, i.e. before serious negotiations have taken place. Thus, like the original referendum vote, it will be taken in ignorance of what leaving the European Union really entails. Critics of Brexit will thus face the charge of opposing “the will of the people” without being able to employ any counter-arguments about the deal being forged.

While Britain’s future is being painted in pastel shades and with a rosy glow, apocalyptic reds and blacks are being applied to a depiction of the future of the United States as President Trump takes office. Perhaps this is because more details are known than with Brexit. The replacement of Obamacare with something “far better”, according to Mr Trump, looks set to disadvantage many millions of poorer, sicker Americans. A new relationship with Russia places Ukraine in jeopardy and undermines NATO. The list of potential concerns is long, but that is Mr Trump’s approach to the future: everything is up for negotiation. He reveals everything; Mrs May reveals practically nothing. Taking a lead from the Presiding Bishop in the US, we pray for both.