UK withdrawal from the EU – Brexit – poses particular challenges for Northern Ireland notably concerning its essentially invisible border with Ireland, an important feature of the peace process. With the EU having committed to finding ‘flexible and imaginative solutions’ during the withdrawal negotiations to address the ‘unique circumstances on the island of Ireland’, the UK and the EU agreed differentiated withdrawal terms in a dedicated Protocol on Ireland/ Northern Ireland. These effectively keep Northern Ireland in the EU customs territory and, through a process of dynamic regulatory alignment, its internal market for goods. A unique but contested status – a ‘place between’ in the UK–EU relationship – has thus been conferred on Northern Ireland. The Protocol has some important shortcomings and implementation poses significant challenges yet also offers opportunities. How the challenges are met will play an important role in determining whether in 2024 members of the Northern Ireland Assembly vote to retain these arrangements. If they do not, politicians and officials will once again be faced with the question of how to avoid a physical hardening of the border on the island of Ireland.