Eurostar immigration checks are done prior to boarding the train. Those travelling from London clear French/Schengen inbound immigration at St Pancras. Those travelling to London clear Schengen outbound and UK inbound immigration in Brussels, Lille or Paris. There is no routine checking of passports by immigration/police on Eurostar trains or on arrival at any stations. This has been the case for a number of years.
Pre-Brexit, Schengen immigration could check only that UK passports were valid - EU freedom of movement prohibited questioning of UK citizens on things like verification of sufficient funds. Post-Brexit, Schengen immigration is *entitled* to check additional items - although this typically happens only if a passenger seems dubious or suspicious. It is worth noting that Schengen arrivals with a non-EU passport will need to be fingerprinted from 2023, which takes additional time. St Pancras departure area is limited on space, so passengers-per-hour processing capacity will be significantly reduced, hence fewer trains can be operated.
The result is that Paris, Lille and Brussels take priority for Eurostar, and London-Avignon trains do not run, leaving a gap in the market for an airline to fly London (City?)-Avignon
Last edited by davidjohnson6; 18th Dec 2022 at 11:59.