Via Somda gevonden op http://www.seat61.com/news.htmEurostar to Amsterdam, more details...
Eurostar's planned London-Amsterdam timetable was revealed last year (see last year's news here) and it's now becoming clear how security checks are likely to work in the London-bound direction for the new service, likely to start this coming December - although Eurostar tell me it's still work in progress.
Passengers will indeed check in at their starting stations in the Netherlands, with X-ray & passport checks performed before boarding at Amsterdam Centraal, Schiphol and Rotterdam, so no need to get off before London. In London you'll just walk off the train as you do now. Domestic Benelux passengers will be able to use the train from Amsterdam and Rotterdam to Brussels, they will not need to go through any security or passport checks, but will board half the 900-seat e320 Eurostar set aside for them. Doors between the London-bound and Benelux domestic halves of the train will be locked shut. When the Benelux domestic passengers alight at Brussels, their half of the train will be security-swept before Brussels to London passengers are allowed on. This is the reason behind the 20 minute station stop at Brussels in the inwards direction, which did indeed seem longer than necessary if nothing were being done, but much too short for the equivalent of the 'Lille shuffle' on the Marseille to London Eurostar, where passengers have to alight, go through check-in and re-board.
I have to say this seems an eminently sensible solution, allowing Eurostar to provide a seamless Amsterdam to London service with no need to alight for passport and security checks en route, as some people had feared. It also allows them to provide much-needed capacity between Amsterdam & Brussels given the failure of the Fyra project a few years ago, and to allocate sufficient space to Brussels-London passengers.