The European Research Group (ERG) of eurosceptic backbench Conservative MPs has released proposals to keep an open border on the island of Ireland.
This is a crucial initiative.
Last December Theresa May made a commitment to a so-called backstop that has bedevilled the Brexit talks ever since, and pushed the UK towards a No Deal Brexit.
The pledge was to have no checks or new infrastructure at the land frontier. Britain somehow managed even to rule out CCTV at the border, becoming perhaps the only major nation on earth to have timidly surrendered such an obvious and elementary right to police the edge of its territory.
Dublin and Brussels have interpreted the backstop as meaning that there can be little or no customs or regulatory divergence, because otherwise there must be checks.
From that moment in December, London has been mostly weak, and the EU largely inflexible.
However, London has in one respect become increasingly emphatic: that there will be no customs border in the Irish Sea.
That leaves open the possibility of a regulatory border, which will be completely unacceptable and the beginning of the end of the UK.
The Ulster Unionist leader Robin Swann is right to be concerned at the ERG failing to be specific about ruling out such a regulatory internal UK border.
Perhaps this is just an oversight. The ERG needs to clarify that.
This is a very serious matter. Mrs May might be unable to get almost any form of Brexit through parliament and the way in which London has been so cowed by Dublin gives an alarming glimpse of what might happen if a chaotic No Deal scenario came close.
The ERG is talking sense and thinking of a way through this but must clarify the regulatory aspect to the Irish Sea.