Pity poor David Davis, who has been made Secretary of State for Exiting the European Union without, apparently, knowing the Republic of Ireland exists.

Appearing on Sky News' Murnaghan programme to discuss the possibility of Scotland remaining in the EU while the rest of the United Kingdom leaves, Davis told viewers that "one of our really challenging issues . . . will be the internal border we have with southern Ireland".

A good point. Indeed; negotiating the border of Northern Ireland will be a challenge, especially given the progress that has been made with–

Wait, what? "Internal border"?

Davis goes on: "we are not going to go about creating other internal borders inside the United Kingdom".

Now, this mole has thought long and hard about this. Why might the minister specifically put in charge of negotiating our exit from the EU not know that the UK shares a land border with a European Union country? Why does he think that the Republic of Ireland is part of the UK? Why is he saying this on national television?

Bit worrying that a British government minister thinks that somewhere called Southern Ireland is part of the U.K. pic.twitter.com/KGltHOCyCU — Plashing Vole (@PlashingVole) July 18, 2016

The answer may seem far-fetched, but after careful consideration, your mole is confident it is the only explanation: Davis thinks the Republic of Ireland is part of the UK, because he is, in fact, a time traveller.

True, it may sound off-key to say "southern Ireland", rather than the Republic. And true, it might seem strange that – just to repeat the above – an actual, genuine minister, who is in a non-fictional cabinet, went on national television and called the border with the Republic of Ireland "internal", out loud, with his real mouth.

But consider this: what if he has travelled through time from the late nineteenth century? What if, through no fault of his own, he has no idea that Ireland has been an independent state since 1922? (In fact, Theresa May may have even appointed him specifically for this reason: for who better to imagine a Britain outwith the EU than someone who in fact cannot remember the EU at all?)

It probably won't be long before we see David Davis poking confusedly at mobile phones, screaming at the automatic doors in the supermarket, and appearing at press events dressed even more bizarrely than most Tories.

If this is the case, it may behove May to find a post-1922 atlas somewhere in the back of No 10 for him. After all, it wouldn't look great if a new cabinet member, who has named securing the UK's borders in the event of Brexit a priority, doesn't know what the UK is.