https://www.newstatesman.com/politics/uk/2017/11/david-davis...
https://www.newstatesman.com/politics/uk/2017/11/david-davis...
UK politicians before referendum pointed out that they were willing to preserve the CTA (common travel area between Ireland and UK) which predated -- but importantly doesn't supercede the EU. Irish politicians pointed this out but were largely ignored by UK press.
>It is the EU that will not allow it.
I suspect you're alluding that this is somehow the EU's fault. It really isn't -- and the finger points 100% at the UK. There are treaties and agreements going back decades including for instance the Good Friday Agreement on which all peace in N.Ireland is largely credited. The lack of a border is mandated by this international and binding agreement which UK seems happy to simply ignore.