When the link up from the ECML was talked about so many years ago now, I thought it would be quite cool to be able to get a train to Gatwick Airport or Brighton - but of course, I'd hardly be doing that very often.
Being able to go on to Farringdon for Crossrail or on to London Bridge might be useful, especially for commuters, but I am starting to wonder whether we really needed the connection given the potential for causing such chaos - as well as managing people on the platforms given so many trains and different destinations and stopping patterns.
I say this because as it stands today, the walk from King's Cross to St Pancras isn't a big problem. There's the subway if you need it, and the crossing could be improved (and perhaps another one installed part way along) if necessary.
The disadvantage is that it obviously means changing train and having to try and make a connection, rather than stay on the train, but the advantage is massive when going the other way - where you can get on an empty train waiting at a platform, instead of trying to board one that could be quite full and having to stand amongst those waiting for other trains before or after.
I wonder if the DfT has factored in how many people will board the wrong trains, and those that will get on and ask 'is this train for ????' despite announcements, screens etc and then hold the doors open to get off?