Within hours of Thursday’s vote to leave the EU, Scottish First Minister Nicola Sturgeon announced her intention to prepare for a second independence referendum. Sinn Fein’s Martin McGuinness called for his own referendum, on a united Ireland.

Only a few days ago, these demands would have seemed unrealistic. But today, the prospect of Scotland and Northern Ireland being taken out of the single market against their will risks leaving the 300 year-old dream of a United Kingdom in tatters.

This kind of balkanisation was never what the Leave campaign intended. Fortunately, there is still a way to stop it. Britain can leave the EU, but remain in the EEA, or single market—following the so-called "Norwegian model".

Remain campaigners have derided this model as carrying all the costs of EU membership, without any of the benefits of a ‘seat at the table’ of EU policymaking. But they have neglected to mention that there are many added perks, too.

The Norwegian model—which also applies to Liechtenstein and Iceland—would fulfil many key Leave demands. Britain would be free of Brussels bureaucracy, and free from the stifling effects of the EU’s Common Fisheries and Agricultural Policies. We would remain a participant in the single market, without any of the trappings of political union.

No longer bound by the EU’s VAT treaty, Britain would have the power to choose its own low rate of VAT to stimulate the economy—a power exercised by both Liechtenstein and Switzerland.

Trade, too, would become more flexible. Members of the EEA, along with Switzerland, often voluntarily work together to negotiate free trade agreements, and the UK would benefit from 26 existing agreements upon joining this grouping. But we would also regain the power to negotiate our own trade agreements—crucially allowing us to re-open the possibility of closer integration with our Commonwealth partners.

Continued access to the single market would reassure investors, and ensure that the City of London remains a global centre for trading and finance, protecting hundreds of thousands of jobs.

Brussels has every reason to accept this solution. European economies would retain access to the British market, leaving the EU to pursue its own project of political integration, free from the conflicting demands of its sceptical former member state.

Of course, EEA membership means continuing to accept the "four freedoms" of the single market: the free movement of goods, capital, services and people.

On Friday, the BBC’s Evan Davis attacked Leave campaigner Daniel Hannan MEP for suggesting that the free movement of people must continue. But there is nothing hypocritical about Hannan’s position. Throughout the referendum campaign, there has been much discussion of the possibility of following Norway or Switzerland, including a feature-length documentary, Brexit: The Movie, which explored these options. This is neither hypocrisy nor a U-turn: EEA membership was always on the table for the Leave campaign.

Indeed, this option is now our best hope for maintaining a United Kingdom. For Northern Ireland, continued free movement would ensure that the Common Travel Area covering the British Isles could continue to exist without border checkpoints. For pro-European Scotland, EEA membership could be a viable compromise capable of quelling nationalist discontent. London, too, would more easily accept a new settlement in which it did not lose its vital lifeline to the European labour market.

Some Leave supporters may feel betrayed by a continuation of free movement. But the alternative is unthinkable. If we leave the EEA, we risk breaking up the Union, and doing untold damage to the economy. The rumblings in financial markets of the last few daysmay prove to be insignificant in comparison to the consequences of a full British exit from the single market.

It is time for the Leave campaign to make clear that ending free movement is off the table, and that this is no bad thing.

At its best, the movement to leave the EU was always about a positive, constructive vision of sovereignty and openness to the world—not xenophobia or pulling up the drawbridge. This positive spirit must guide the country’s next steps. That includes recognising that free movement brings not only costs, but real benefits, too.

Freed from the political superstructure of the EU, we now have a chance to articulate a new vision for Britain’s role in the world, including our relationship with the Commonwealth, as well as rising powers like China. But membership of the EEA must be central to this vision. If it is not, we risk not only our prosperity, but our very existence as a United Kingdom.