Paul Scott wrote:

I don't think you've got this right Jack; in the LB Camden planning
info, there is a document that discusses all the details of passenger
movement. It shows quite clearly that the overbridge will be a one
way route onto the platforms for departures, but that the main
passenger flows will be to/from the south (existing) end of the
platforms, and mostly onto the forecourt:

Apologies if I was unclear. My understanding was based upon articles in the
transport magazines, I hadn't actually seen that very interesting document
that you link to, and was that all departures will take passengers into the
station through the new west side ticket hall, feeding them to the first
floor waiting area and then across the new (as you say, one way) centre
footbridge and then down to the platforms by lift or escalator. Following
demolition of the current 'temporary' mess at the front of the station to
reveal Cubitt's facade, I was under the impression that this would be the
main point of exit from the station for all passenger arrivals (apart from
those, I assume crossing to St. Pancras domestic platforms). The suggestion
was that there would not be access to the platforms from the front of the
station - perhaps things have changed since, following consultation.