If we need (and I still think we won't) Visas - and probably certainly to fill in ETIAS forms, what will the procedure be @ St Pancras? As far as I know passports and tickets are checked this side of the channel, thus someone with the wrong docs couldn't travel. However, especially r/e visas, how long will it then take to process a queue, especially if a couple of pax's documents aren't in order? And what if the first country of stay is Holland or Germany yet we have to alight in Belgium and maybe even leave the station to catch a coach or something?
Perhaps a Brexit voter knows all the answers?
an ESTA style document may be a possibility, but there are some countries where you don't even need those.their immigration deparments will already profile in advance,and you turn up at the border control on landing and get issued with a 3 month temporary visa automatically at the booth.
this is a legal document and must be presented along with your passport at places like hotels etc when booking accomodation,or hiring a car etc.
it's very easy.
just book flight/train 24 hrs in advance and submit passport details at the time of booking.
I would recommend you bringing either a business letter of invite or your holiday schedule to show the customs official if they ask you about the nature of your visit.
If everything goes smoothly then it should take no longer than an extra 20-30 minutes for the processing at border control(mostly down to slightly longer queues)...mostly on the arrivals side I should add.
if you are not permitted to enter you would get told when you tried to check in.
as for st pancras to germany via belgium, then the first port of call is still france and they will do the relevant checks,after that it is schengen.
the system would be like swedish customs checks on the oresund train.no need to alight.(process takes 20 minutes or so.)
1)alight kastrup airport(copenhagen)
2)board train to sweden
3)train will cross oresund bridge and stop at hyllie station
4)customs officials board train and check documents
5)departing passengers alight, onward passengers stay
6)customs officials alight
7)off you go!
on our side, they might extend ashford international or ebbsfleet with a couple of extra tracks/platforms for holding trains, and customs checks could be carried out there on inward trains.