Train passport control from London to Paris
I'm a non-EU citizen, I will be travelling from London to Paris next month, so I was wondering since most countries track entry and leave dates, if I use the train to switch these countries and they don't control it, my UK visa will seem like entry YES but no leaving. Same for the Schengen, I wouldn't have an entry date but I'll be leaving,
Will it be trouble later? Are they controlling this on trains? If not is there anything I should do before?
Travelling from London to Paris by Eurostar, you'll go through checkin, then security, then (as of 2015) a Eurostar-run UK exit check, then finally French Immigration. You won't see anyone from the UKBA, but you will see someone from Eurostar who'll scan your passport and send UKBA the details electronically, but won't stamp it. The only people properly checking your passport + stamping it if required will be French.
Travelling from Paris (or Lille) to London by Eurostar, you go through checkin, then French exit Immigration checks, then UK entry Immigration, then security.
The UK does not have formal exit immigration controls, but the UKBA do receive details of who goes from most transport providers. In the case of Eurostar, that's done by a member of Eurostar staff scanning your passport with a nifty handheld reader between security and French immigration.
France, following Schengen rules, does have formal exit immigration, with checks done by immigration staff.
So, UK -> France by Eurostar your checked "entering" France in London, France -> UK you're checked "leaving" France then immediately "entering" the UK (all in the station). All "entry" checks are juxtaposed border controls.
One more thing, if your train is from Brussels and you board at Lille you will be checked again in London, but is a more easy one. Tickets and passport only.
@DumbCoder Not since they agreed to herd all Brussels to Lille passengers into only carriage 18 you won't, not unless they loose someone from there. Thankfully, the extra border check in London for Brussels/Lille is now a very rare occurrence (and I speak from experience!)
+1, very nice. Minor nitpick, the UK introduced formal exit controls last April. Please see http://travel.stackexchange.com/questions/43808/is-the-uk-planning-to-introduce-exit-checks-in-2015
@GayotFow They're not UKBA-run exit checks though, but transport-provider run ones, and they're not quite comprehensive. That's why I didn't call them formal ones, as unlike Schengen or Australia it isn't an immigration offer checking you out
@Gagravarr, last nitpick, UKBA doesn't exist any more. It was disbanded after the scandal http://travel.stackexchange.com/questions/49195/uk-immigration-control-which-queue-for-eu-non-eu-couple-travelling-together/49198#49198 Current answers should use UKVI, but same outfit anyway
There is no check on the train like there used to be between other EU countries or Switzerland before Schengen. There is a full airport-like passport and security check at the train station so you will get Schengen entry/exit stamps every time (I don't know exactly how UKBA tracks exits but I don't think they stamp passports on exit).
In fact, standards regarding external borders were part of the Schengen agreement from the start so there are very few borders where this can realistically be a problem (I have heard about Andorra or Gibraltar…). In that case, you can always try to approach the border police yourself or keep any material evidence that documents your presence in and out of each country (including the train tickets).
There are no UKBA staff at St Pancras on the departures side, only French immigration staff checking passports. There are UKBA staff at St Pancras, but they're all on the arrivals side, where they sometimes pop out for spot checks
I boarded Eurostar today London>Amsterdam (via Brussels) and the EU did not initially but obliged when I asked for an exit stamp. So the Exit stamp is possible if requested.
@ScottCate From who? The UK reinforced exit checks after I wrote my answer but they do not involve a stamp AFAIK. The only border guards you see when boarding at Saint Pancras would be Schengen (French or possibly Belgian or Dutch) border guards and what you get from them is an *entry* stamp. If you are a US citizen and not married to an EU citizen, that stamp is mandatory, you should not have to ask.