Since we were on air, there have been some interesting developments in Belfast, which bear on some of the issues we discussed. Taoiseach Leo Varadkar and Prime Minister Theresa May have agreed to work together to focus on achieving a border solution based on the future relationship between Britain and the EU, Option A in last December's withdrawal deal, to avoid having to implement Option C, which would provide for specific regulatory alignment across the island of Ireland, in areas related to the Good friday Agreement.
The difficulty for May was highlighted in a recent post by the BBC's John Campbell:
Effectively, the UK will be asked to sign up to a legal agreement where alignment will be the default option.
That default will only be overridden if a better solution can be found - with the EU presumably acting as arbiter of what is "better".
There is potential political danger here - will that arrangement be acceptable to the majority of Theresa May's cabinet?
My reading is that today's agreement is about de-emphasizing that default option to make it more palatable to the British Government, without necessarily conceding on the substance.
If a withdrawal agreement including Option C is signed early this year, it could be a powerful constraint on later stages of the Brexit process, pushing the UK as a whole towards a closer relationship with Europe.