Theresa May’s attempts at a further climbdown over the Irish border have run into trouble both among Brexiteers in her own party and her DUP allies. Her new proposal reported yesterday would see the whole UK remaining in the customs union beyond 2020 – “until” an Irish border solution that satisfies the EU is found. Many Brexiteers are surmising that this may well be never…

The DUP have been even more exercised by the other part of the plan which would create regulatory divergence and checks between Northern Ireland and the rest of the UK. After hitting out in an interview yesterday, Arlene poured further woe on May’s plan this morning, telling Today that the DUP’s red lines on the issue remained “blood red”:

MH: “It’s a question of how red your red line is?”

AF: “The red line is blood red, it’s very red.”

MH: “Then you would be prepared to walk through the lobbies with Jeremy Corbyn?”

Foster – a passionate Unionist – even refused to rule out voting with the IRA-sympathising Jeremy Corbyn in order to defeat any plan which involved carving off Northern Ireland. If May underestimates the strength of DUP resolve on the issue it could be fatal for her attempts to get a deal through…