Ministers Davis, Fox and Johnson are pressuring PM Theresa May to abandon her proposal for the UK to collect import tariffs on behalf of the EU, while allowing the UK to negotiate trade deals with other countries. Their concern is that this approach creates a slippery slope that could result in the UK remaining in a customs union with the EU. (If that were to happen, what will have been the point of Brexit?)

Instead, the Brexiteers favor a "maximum facilitation" customs option which would minimize but not eliminate customs checks - and which would make it impossible to have a totally open Ireland-NI border.

Reverting to a pre-Good-Friday-Agreement closed Ireland-NI border could have a devastating effect on tourism in both countries.