Jonathan Powell: Backing the People's Vote is DUP's best chance of preventing united Ireland
Brexit was always going to trample on someone's rights. If the United Kingdom was going to leave the Customs Union and the Single Market then there had to be a hard border somewhere.
At first Boris Johnson proposed it should be between Northern Ireland and the Republic, which would have injured the identity of nationalists.
The DUP made the mistake of trusting him to stick to this approach, despite his track record for duplicity.
In a panic to achieve Brexit by the October 31 deadline he had set himself, he ditched them and surrendered to the EU's demand of a border in the Irish Sea, something Theresa May had said last year 'no UK Prime Minister could ever accept' whilst Johnson nodded alongside her in the Commons.
It should come as no surprise that the DUP have now opposed his deal, fearing it is the beginning of a slippery slope to a united Ireland.
And they have a point. The border in the Irish Sea will grow wider over time as the UK diverges from EU rules on regulation and introduces new and different tariffs.
More and more goods will be added to the list of those that need to be checked, which will be agreed by a joint committee with the EU.
Please log in or register with belfasttelegraph.co.uk for free access to this article.
Reassurance on this issue by the British government has always been crucial for unionists.
Tony Blair's first visit outside London after his election victory in May 1997 was to the Balmoral agricultural show.
Amongst the prize bulls and sheep he made a speech in which he said he did not expect to see a united Ireland in his lifetime.
That undertaking helped to reassure unionists as we went into the negotiations that led up to the Belfast Agreement.
They can no longer be so sure.
Opinion polls show that, as a result of Brexit, the 30% of Catholic voters who traditionally support remaining in the UK has been driven down to 10%.
Demographic and other shifts are likely to drive it down still further when they have to choose between the UK and the EU. Once the numbers start getting close to 50/50 the British Government will have to hold a border poll.
Boris Johnson also promised the DUP a veto on the Brexit arrangements. This would have been wrong.
The peace process is a see-saw, and the British Government should stay in the middle rather than jumping on one end or the other.
It should have been for a majority of both communities to make the decision. But instead of remedying it in a way consistent with the rules at Stormont, he has agreed to a vote by simple majority in the Assembly.
The trouble with this approach is that it undermines the whole basis of cross-community decision making under the Belfast Agreement.
Already people were questioning the power-sharing formula and arguing for a return to majority rule.
If it is right for one important issue why not for others?
The DUP are not powerless in the face of Johnson's treachery.
They were crucial to the success of Oliver Letwin's amendment on Saturday and they will be key players in the Westminster arithmetic over the next few weeks.
They can use their weight to try to stop his deal.
Their first demand is naturally that the deal should be reopened straight away but the EU is unlikely to countenance that.
Instead they can propose amendments to the legislation implementing the deal and support the amendments of others, including the Kyle-Wilson amendment requiring a confirmatory ballot on the deal.
If such a referendum were to take place then the vote against in Ulster, uniting both nationalist and unionist opposition, would be likely to be far higher than the 57% last time.
Johnson's rhetoric about a democratic solution in Northern Ireland would be difficult to square with imposing a deal universally reviled in the province.
It may therefore be that the DUP's best chance of preventing the outcome they fear is to support a People's Vote.
Jonathan Powell was Tony Blair's chief of staff from 1995-2007