Christopher Howarth is a senior researcher working in the House of Commons. Prior to this he worked for Open Europe, as a Conservative Foreign Affairs Adviser and senior researcher to a Shadow Europe Minister.

Customs posts were first introduced on the Northern Irish border by the newly independent Southern Irish Government on April Fool’s Day 1923. Most treated them as a joke, except for one group of diehard republicans who burnt one down three days later. They lasted until 1993, when the creation of the Internal Market removed their last significant role.

It is now as clear as crystal that the UK will leave the EU’s internal market and move outside EU’s external customs wall. The logic for this is something I first explained on ConservativeHome here. The Government, understandably, has decided not to rule anything out for now. But we should assume it will do so when it sets out its stall, shortly before the activation of Article 50. The direction of travel is obvious, however, and has the full force of logic: if we want to have a meaningful international trade policy, we cannot remain inside the customs union. This is the right choice, the only possible choice and one that allows the UK to gain the benefits of Brexit.

For the UK, this again raises the issue of the Northern Irish border, a border that is currently customs-free. During the referendum campaign, the Remain camp tried to make political capital out of the potential changes, wheeling out Major and Blair to make the implausible and scurrilous claim that Brexit could harm the peace process.

These hysterical concerns have thankfully died away, but there remain questions to be answered. These come in two parts: firstly how to deal with the customs control of physical goods moving across the border and secondly policing any new UK immigration policy that seeks to restrict EU workers.

Let us take physical goods first. Outside the EU’s customs union there will need to be some form of customs controls. The image this conjures up is of tailbacks of cars being searched for contraband. This is in nobody’s interest and will not happen. It is in both the UK and Southern Ireland’s interest to introduce controls with as light a touch as possible. This will no doubt mean excluding the vast majority of crossings made by car, as is the case on the Norwegian/Swedish customs border where checks are sporadic and in effect limited to a few designated crossings. Following this model it will also only involve one set of controls, as the UK and Ireland can operate the controls jointly.

For goods crossing by lorry, there will be more checks. However, movements of goods across a border are generally predictable and can be cleared in advance. The Transports Internationaux Routiers (TIR) can be used to allow this to happen in Northern Ireland. As a House of Lords’ report of yesterday argued this will be “subject to the agreement of the EU institutions and Member States.” This will need to be negotiated, but with goodwill, a cooperative EU and a mixture of the light touch de minimis thresholds, quotas, joint clearing and technology it will still be possible to cross the Northern Irish border without noticing. There is no reason to suppose the EU will stand in the way.

The second issue is the free movement of Irish and British citizens. Ireland and Britain have had a Common Travel Area for many years, which allowed for common citizenship and the continuity of passport free travel post-independence. This is allowed under EU rules because Ireland, like the UK, has a Schengen opt-out. This arrangement survived the Second World War and the Troubles, and it will survive Brexit.

The more complicated issue is the free movement of EU citizens into Ireland to work who then cross the border into the UK. This could be argued to be a back-door into the UK labour market. However, this need not be the problem it is made out to be. EU citizens will no doubt be allowed into the UK visa-free post-Brexit, making the Northern Irish route slightly superfluous.

An EU citizen arriving via Northern Ireland and overstaying will be in no different position to an EU citizen arriving via Heathrow. While the right to work in the UK may be curtailed, it is likely that control will not be exercised on the border via visas. Intelligent co-operation on the Northern Irish border will again help maintain the free flow of Irish and British citizens. Given we already have a Common Travel Area we already share information under a memorandum of understanding with Ireland on immigration cases. This can continue. There is already co-operation on cross border working of EU migrants with Irish police helping UK police disrupt EU citizens illegally working cross-border.

The recent history of the Northern Irish border has waxed and waned. From the 1930’s to the 1950’s trade protectionism in the south led to real price differentials, initially not helped by a tit-for-tat trade war. Yet throughout the period the UK and Ireland maintained a free travel area and a de facto currency union. When the UK and Ireland both joined the EEC on 1 January 1973 the EEC’s main benefit on UK/Irish relations was removal of tariffs in a way that had proved politically impossible on a bilateral basis.

However, the EEC has not always helped UK/Irish coordination – in effect it was responsible for breaking the currency link. When Ireland joining the EEC’s European Monetary System – the Snake – in 1979 and the UK stayed outside, the two currencies, first linked as far back as 1210, diverged. With Ireland’s decision to join the Euro, the Irish border became an Eurozone frontier, on the one side the Eurozone, its currency and economic policies on the other the Pound Sterling.

Maintaining a light-touch border will undoubtedly be subject to negotiations involving Ireland and the EU, however the doom-mongers of remain have already been proved wrong. Irish/UK relations have weathered many storms. Brexit need not be another, even if the EU refuses to agree free trade with the UK and reintroduces tariffs.