I noticed when taking the Eurostar to Paris last December that you had to clear security as well as passport control before boarding the train. However, when I took a Thalys train from Paris to Brussels and then Amsterdam, no security or passport control was required.
My question is, why is security and passport control required for the Eurostar but not for Thalys. Both are international trains going between EU countries. Is it because there's a higher risk of attack due to the long tunnel ride in the Eurostar?
That said, the Eurostar was fantastic, and I can't think of a better way to get between Paris and London. Can't wait for the British high speed link to open this summer!