Of all the obstacles to the government’s preferred Brexit plan, the Irish border issue remains the most intractable.

May’s government remains committed to leaving the EU’s single market and customs union, but simultaneously maintains that there will be no border infrastructure between Northern Ireland and the Republic of Ireland. These two positions seem mutually exclusive. If the UK leaves the customs union, there needs to be a way to check controlled produce leaving the UK which will necessitate border infrastructure to facilitate customs checks. If the UK wants to control immigration from the EU, it will need to set up passport checks on the Irish border.

In reality, it seems that there are three options. The first is that the UK leaves the EU’s single market and customs union, creating a hard border between Northern Ireland and the Republic of Ireland. This option is not palatable to many in Westminster who fear that it would jeopardise the peace process in Northern Ireland and it would clearly be disruptive to those in Ireland who currently travel across the border for work.

The second option is that the UK remains within the EU’s customs union and continues to allow the free movement of people. Given that two of the government’s main objectives for Brexit are to gain greater control over immigration and to achieve the freedom to make trade deals with other nations, this option would be impossible to sell politically to the party’s right wing and to its membership.

The final option is one formalised by the EU in its recent legal paper on the matter: border checks between Ireland and the UK. This would see Northern Ireland effectively remaining in the customs union, apart from the UK. This would be an intolerable situation for Northern Ireland’s unionists, and would almost certainly see the DUP remove their support from Theresa May’s minority government.

For a government committed to both a hard Brexit and no hard border in Ireland, there is clearly no good option. What then will Theresa May’s government try to do?

It seems likely that the Conservative Party will try to pursue some variant of the first option but will attempt to present it as a fourth option to play down the ‘hardness’ of the border. In August 2017, the government produced a position paper on the Irish border which suggested that, instead of traditional customs checks and passport controls, the government could operate a technological tracking system for goods. While this system is wholly untested, it would almost certainly mean that there would be physical border infrastructure, but it would be less visible than the alternative. The system may operate similarly to the Swiss-French border where cars are spot checked based on calculations of risk and ongoing investigations but most of the time people can freely cross the border. Under the Swiss system, cars from France crossing the border can be stopped and checked many miles inside Switzerland, making the border seem less fixed and defined, something that could be attractive to opponents of a ‘hard’ border.

This scenario does have drawbacks of course. If passport checks are not standard, it allows an easy route for illegal immigration into the UK. The government’s stated position in its position paper is that this kind of border may require regulatory equivalence in terms of farming standards with the EU, which would be a significant point of contention in any future UK-US trade negotiations. While people and cars would be able to travel relatively freely between the two countries, lorries would likely be subject to more stringent checks, leading to long queues and less efficient trade between the UK and the Republic of Ireland.

And finally, the EU may not acquiesce to such loose border arrangements between the UK and its customs union, especially given the untested nature of the technology. The EU or Ireland may also see these plans as just another version of a hard border, something they consider wholly unacceptable. This means that, while a loose border may be May’s preferred option, it is by no means the most likely at this stage.