IME the ferries (and Eurostar) have exported borders. To go from Dover to Calais, you first go through both British and French passport controls. And the same going the other way.
The difficulty is not with passport checks though.
The difficulty is with customs checks. We can't just wave through freight and cargo from the EU unless we do the same with frieght and cargo arriving from everywhere.
To do so would be a violation of WTO trading terms.
Oh absolutely. I was just responding to a series of posts from Aber specifically relating to people rather than goods.
Yes, the customs system will come under considerable pressure (to put it mildly). Apparently there is a new IT system in the works (which is worrying enough given government "expertise" with large IT systems) which is due to go live around Brexit time.
Reportedly it's able to cope with the expected five-fold increase in customs declarations but I'd take that with a large pinch of salt. Anyone with a lorry park in the Calais or Dover region is going to be doing good business