It’s not all about us.

Brexit means Brexit. Theresa May has made it clear that it is she who will ultimately decide what that means. But the prime minister is deluding herself. And I’m not convinced that, despite the recent high court ruling, the House of Commons is about to shape our negotiating strategy. Our fate lies not only in the government’s hands, but also in those of our European partners.

This is all down to the rules of the game. Forget article 50. The real issue is that the deal that the UK strikes with its partners about our future economic relations with the EU will require unanimous ratification, not by leaders meeting in the European council but, rather, by parliaments across the EU (of which, if you include those regions with voting rights, there are 38).

Hate crime inquiry head warns against 'whipping up prejudice' in campaigns Read more

Many, if not most, of the other member states enjoy pretty healthy levels of trade with the UK. This provides an economic incentive for all parties to come to an amicable settlement that preserves these economic relations. Jobs are at stake on the continent too.

Unfortunately, however, economic rationality does not always win the day when it comes to political decisions. Just as, for some in this country, the principle of restoring British sovereignty trumped issues of profit and loss, so too, for some of our partners, issues other than economic advantage might determine their reactions to Brexit.

In an attempt to understand continental attitudes to Brexit for a BBC Radio 4 programme to be aired this evening, I took a short trip and talked to politicians in four member states – the Netherlands, France, Germany and the Czech Republic – where elections are due next year. Not a representative sample, certainly, but enough to give an impression of the incentives that might shape the Brexit negotiations to come.

It should come as no surprise that one person celebrating the referendum outcome was an MEP from France’s Front National. Having described how he had popped open the champagne on 24 June, however, he quickly added that his party’s glee would work against May.

The challenges May’s plan will face include France’s centre-left and centre-right politicians having no interest in allowing Britain an exit deal that strengthens Marine Le Pen. And their desire to send a political message is shared by centrist politicians in the Netherlands, nervously tracking the electoral prospects of their own populist firebrand, Geert Wilders. The Dutch traditionally may have been a close and reliable ally of ours in the EU, but politics is politics, and an attractive Brexit deal is not in the political interest of the governing party.

For politicians in the Czech Republic, it is the threat to their countrymen rather than to the political centre that preoccupies the political class. Reports of increased levels of violence and abuse towards eastern Europeans were given prominence in the domestic press, and political leaders have been quick to promise to do all in their power to address the issue.

And it is against this background that they will approach negotiations with a British government keen to secure as much trade with the EU as possible, while controlling migration into the UK. And here, the Czechs draw a line. Freedom of movement is one of the key attractions of EU membership for the people of central and eastern Europe. Diluting the principle to help London is, to say the least, not a high priority in Prague at the moment.

Which brings us to Germany. The high volume of trade that Germans enjoy with Britain has convinced many in this country that Angela Merkel would not be willing to impose economic pain on her country by insisting on a Brexit deal that imposed barriers to commerce. Surely, so the argument goes, the big German manufacturers will lobby hard to preserve access to a key market?

But to think this is to mistake the mood in Berlin. A senior official from a prominent employers’ association told me ruefully that his members were already suffering ill effects from Brexit. However, frantic efforts to persuade the German government to limit this pain were proving fruitless.

An MP from the governing CDU explained why. As far as Germany’s government is concerned, the challenge of Brexit is akin to that of dealing with Russia after its invasion of Crimea. Then too business leaders warned of economic pain if sanctions were imposed on Moscow. But the government held the political imperative to be more important than the economic calculation. This, he added with someone finality, would prove to be the case in negotiations with London as well.

EU ministers to discuss plan to charge Britons to visit Europe after Brexit Read more

And it is not just in Berlin that politics will trump economics. The Dutch equivalent of the Office for Budget Responsibility has predicted a loss in the region of €10bn over the next 15 years in the event of a “hard Brexit”. The Dutch government is simply incorporating the figure into its economic planning. My Front National friend explained, with some bitterness, that the French elite was willing to risk French jobs to protect the EU and undermine the prospects of his party in next year’s election.

For all the differences in their domestic political situations, our partners are, for the moment at least, united when it comes to the Brexit negotiations. And this is seen most clearly in their hostility to the idea that the UK should be allowed to benefit from the single market while restricting freedom of movement.

This is not borne out of any desire to punish us. Everyone I spoke to was genuinely sad that we have voted to leave. But ultimately they all acknowledge that their own interests, whether they be domestic politics, or in ensuring the stability of the EU, take precedence over their friendship with us.

Of course, there is a long way to go until the negotiations start, let alone finish. And politics, especially contemporary politics, has a habit of surprising us. Nothing about Brexit is preordained. But, from where we stand now, we don’t just need a post-Brexit plan, we need to overcome the attitudes of our partners, or it is likely to be an economically painful ride.

• Analysis, Brexit: What Europe Wants, will be on Radio 4 this evening at 8.30pm