It has been a consistent feature of Brexit that its principal cheerleaders appear to have only a dim understanding of what it might realistically entail, and moreover that they appear to assume that firm commitments made in consequence on negotiation with the EU can be lightly cast aside when they are seen to unsettle the preferred narrative of a Brexit crafted on British terms.
Interesting article on the NI Protocol here on the EU Law Analysis blog.
Irish waterways history 