Are you talking about the Eurostar service from London (I remember the Waterloo station, though I hear it has moved to St. Pancras). That's the only one I can think of that fits your description.

The Thalys from Cologne to Paris via Belgium is/was also simple walk on walk off with normal train stations.

I don't doubt they keep those manifests, but I've found very little actual control.

Brussels does have troops going around, which is unsettling, but I never saw them inside the actual station, nor stopping people entering it, even after that poor devil immolated himself last year.