The key to delivering soft Brexit has been staring us in the face

“Kick out European Union migrants after three months if they can't find jobs after Brexit” is not, admittedly, a typical Remainer headline. But peer closely at it and you can see a clue to how soft Brexit could be delivered.

It was tweeted out last month by the Sun newspaper, as part of a story on business needs after Brexit. The content matters less than the tone, though. The important thing is that it sounds tough, appropriate for a snarling anti-immigration red-top tabloid and the kind of thing Leave voters want to hear. It is also completely consistent with staying in the single market.

In 2010, a 25-year-old Romanian woman called Elisabeta Dano travelled to Leipzig with her son, and moved in with her sister. She didn't know it yet, but she was going to play a small but important role in Europe's constitutional history.

After a year or so, she applied for benefits, but the Jobcentre refused her. She could speak German and was fit for work, they pointed out, but she hadn't looked for a job. They weren't having it. She issued a legal challenge against the decision to the local court. They passed up a few questions to the European Court of Justice (ECJ) which amounted to a stress-test of free movement rules.

What does free movement mean in practice? How extensive a right is it exactly? After all, the Treaty of Rome, which founded the EU, does not mention freedom of movement—it mentions freedom of labour. You can move countries to work, but that right is subject to tests.

The European court found that the German authorities had behaved within the law. It was a decision with far-reaching repercussions. Domestically it kept a lid on complaints about free movement. Had the court ruled the other way it would likely have boosted those complaining about immigration to Germany.

But importantly it also clarified the rules on free movement: you have three months to find a job when you move to another EU country. After that, you need to show that you have the funds to sustain yourself or it's time to pack your bags. There was no legal requirement for the state to pay you benefits during that period.

It remains, to this day, an utter bafflement that David Cameron did not make more of this case. For all his complex wrangling about limiting benefits for migrants in his pre-referendum negotiation with the EU, this case did most of the heavy-lifting for him. He could have come back with a deliverable domestic agenda about enforcing the three-month rule. Instead, he barely mentioned it. Maybe No 10 thought European court judgments sounded dodgy and foreign, even when they were in its favour. Maybe it didn't realise the implications. Either way, it was a bit of political arsenal designed by fate to shoot down Brexit arguments and Cameron chose to neither pick it up nor fire it.

Even after the referendum, this could have been used to save Britain from the embarrassing drunken state it has fallen into. As everyone now knows, free movement is a condition of single market membership. It is Theresa May's decision to end free movement, above any other political consideration, that means we have to leave the European Economic Area and put livelihoods at risk.

The Dano case highlights how unnecessary this all is. A leader with resilience, communication ability and vision could have worked within that system to deliver reform of free movement. Domestically, without any negotiation with the EU, she could have imposed a strict three-month time window for EU migrants to find work and combined it with exit checks at the border. This last part is a long promised policy, even during the Coalition.

At a European level, it would have been easy to negotiate a four year benefits lock on new migrants, indeed Cameron had already secured it. If the PM was really canny she may have been able to secure additional measures, like the fabled “emergency brake” keeping numbers below a certain level for a few years. The provisional nature of that kind of measure might have made it palatable in Europe.

Some at the time, including former deputy prime minister Nick Clegg, reported that the Germans were waiting for May to make these kinds of overtures in the wake of the vote. She never did. After all, it would have been a hard sell. Plenty of elements in her party would have been fuming. And May tends to buckle whenever the right of the Conservative Party demands something.

But it would also have been in keeping with the Brexit mandate to leave the EU and what we know of the Brexit vote itself. A consistent minority of Leave voters—the figure hovers between 20 per cent and 40 per cent—are either unfussed by immigration or prioritise economic issues over its reduction. Combine that with the Remain vote and you have no majority on ending free movement.

That Sun headline tells us what was manageable in terms of press reaction. You can frame this kind of extensive domestic and international reform as a strict root-and-branch reform of free movement. Ideally, you would also rebrand it, perhaps as “fair movement.” This was a doable political project of the type a more confident and sensible leader would have adopted.

Instead, May did something very different. She got on stage at the 2016 Tory Party conference and promised to end free movement and ECJ jurisdiction and even foreign rules on food labelling. The last part is so extreme you'd have to leave the World Trade Organisation if you really intended to deliver it.

She had no idea what she was saying. Neither she nor Nick Timothy, her adviser, had any idea what the implications were of the rash promises they were making. They just scribbled them down on the back of a napkin and read them out, to get them out of that day's bind, just like years before when Cameron had promised a referendum because he might lose some seats to Ukip. This is the type of short-termism which defines the methodology of the modern Tory Party.

The Sun headline tells us how readily we could have pursued another path, accepting the Brexit mandate, addressing concerns on free movement and protecting the economy at the same time. Unfortunately, it requires a political class with bravery and understanding—a notion which at the moment feels like utopian sci-fi.