A new volume of essays laments the lack of support for the Union from anywhere outside Northern Ireland.
If he cannot or will not convince them that its guarantees of their British status are real and meaningful, its days are numbered.
His extension of grace periods only makes sense as part of a strategy aimed at securing meaningful concessions to assuage unionist concerns.
A December election in Northern Ireland could therefore turn, in a manner of speaking, into a referendum on the agreement.
The best way forward might be a statute of limitations on past conduct that covers the United Kingdom as a whole.