Politicians who want to unite Ireland under a Dublin-based government are stuck choosing whether to participate in the UK in an effort to stay in the EU.
Why much of the fate of the Irish border lies in the future of the UK's customs arrangements with the EU.
From trade to medicines, the UK government's 'just in case' planning is revealing.
Brexiteers keen to follow Norway's example face an awkward dilemma.
The difference between a customs union and a free trade area – explained.