I have just returned from a trip to Germany using Eurostar and DB.
The checks at Midi on the way out are as follows: a man standing between you and the escalator, yelling "PLF s'il vous plait!" and then looking at a QR code on your phone. The QR code could be of anything, mind. The check was extremely brief, but that was about it.
On the way back to the UK, however, the full passport control and documentation check applies.
Belgium make it clear as mud with the regulations, but to visit Belgium on Eurostar you do need:
- a clinic-certified negative LFT or PCR test for your outbound travel
- a clinic-issued LFT (with online verification, not just an NHS one you do yourself) to take while away before you come back
- a PCR booked after your arrival back in the UK
- a passenger locator form for Belgium, completed
before you travel out (this is checked in the UK)
- a passenger locator form for the UK you'll likely have to complete while away, due to having a 48-hour expiry
- for onward travel to Germany, separate PLF forms for each direction in Belgium, and a separate PLF for Germany (the latter was never checked)
- your covid pass showing proof of vaccination with both doses and an ACTIVE QR code (the QR codes expire after 30 days so make sure you don't have an old PDF / printout)
- your usual travel documents, passport I assume
- your Eurostar / DB / whatever tickets of course
Note, I know that as a transiting passenger I still need to fill in the PLF but a pre-departure test is not required for Belgium.
I need to state, this is NOT correct. This caught me out too as I believed this to be the case, but Eurostar would not allow you to enter security at St Pancras without a negative departure test due to recent changes to Belgian restrictions not listed on either the Eurostar or the gov.uk website, ye be warned!
No checks were made on my train from Brussels to Cologne with Thalys, but it was a busy evening peak train, perhaps that is to be expected.
Covid pass & PLF checks were made on the DB train from Cologne back to Brussels. People that didn't have a PLF didn't seem to be impeded in any way, but were warned that they could be in trouble later in their journey.
I think that covers everything? (I'm obviously not liable if I've left something out or if it's changed again by the time you travel!) It's a real hassle, honestly, which is a shame as otherwise, getting the train into Europe and back would have been really quite easy.