Originally Posted by
ls17031
You're assuming it wasn't a UKBF device just like the one which was used to scan my passport upon my departure on the Eurostar at St. Pancras in December. Passport reader attached to a handheld device. If it's anything like the devices I'm familiar with it can be used to query databases and peruse passage and travel history.
OK, I reread the OP and he did say that it wasn't necessarily the passenger's phone.
I think the Eurostar devices just scan and record the MRZ. Those are private Eurostar employees so have no business querying government databases, but you may be right, UKBF staff may possess mobile passport scanners that link to their computers.