Steve,
We have threatened the border.

No we have not. Our government says unequivocally, under no circumstances will it make any changes to the border.
EU threatens that it will, not us.

DMcG
I see it as a message to BOTH sides that there is something of great importance there beyond the economic and BOTH sides need to be wary of how whatever they propose might alter that.

It is not "BOTH" sides proposing to alter that. Just EU.