I agree that the open border is important for those on both sides. Personally I was hoping that the political leaders of both the UK and EU would start the negotiations by aiming for common ground and establishing some good faith, and the Irish border would surely be one of the areas where everyone could agree a high degree of openness was in everyone's best interests. Alas, they seem to be doing the opposite so far, and now we have this new spanner in the works.