Professor Tamara Hervey:

As it is not a legal question but a political question it is very difficult to tell whether the EU would reopen the whole withdrawal agreement. There is nothing in Article 50 of the Treaty on the European Union that legally prevents the EU from doing so but the politics of it suggest that the EU will not. The EU has other problems that it needs to deal with and it wants to move forward. The EU wants to have its relationship with the UK put safely into a box called negotiations with third countries so that it can move on to dealing with the other things that the EU needs to deal with.

I am surprised at the notion that an extension of the transition would be almost guaranteed because it must be legally agreed between the EU and the UK. No one side can guarantee an extension, legally speaking, but the politics are extremely difficult.

The one other thing that I will say is that the longer there is no Brexit the easier it is for the EU, as a whole, to prepare for a no-deal Brexit. That does not help the areas of the EU, like Ireland, that are particularly vulnerable to a no-deal Brexit but it does give the EU more time to put law and logistics into place. If we had had a no-deal Brexit in March it would have been significantly worse than a no-deal Brexit in December 2020 would be.