Unfortunately that is the sort of thinking that guarantees that London will continue to dominate our economy for employment and income. Don't you think the "population levels" might actually be a consequence of the funding that has been put into London's infrastructure over the last half-dozen decades?
I would say it's more the kind of thinking that will ensure that HS2 actually gets built!
And I was referring to the combined population levels of London, Liverpool, Manchester, Newcastle, the North of England: Basically everywhere that trains heading NorthEast out of Curzon Street will be going to. The point is that, even some through platforms were built, you'd probably still be seeing no more than, maybe, 20% of HS2 trains heading SW, and therefore potentially needing through platforms.
And no, I think the population levels in London are largely a consequence of our economy becoming more and more specialised, which leads to job roles becoming more and more specialised. That means that companies need to recruit their staff for certain specialist roles from smaller and smaller groups of people. That leads to companies moving to the places with the highest populations, because that's where they'll find the specialist staff, and that sets up a vicious cycle where more and more people also want to move to the biggest cities because that's where the highest paying companies have moved to, and you end up with this awful cycle of the largest cities becoming larger and larger. To add to that, young people are far more mobile these days than in times past, and most young people tend to want to go to places where there are already lots of of other people and therefore lots of culture, lots of jobs, lots of dating opportunities etc. etc. The whole thing is a cycle that - as far as I'm aware - virtually no Government anywhere in the World has so far found a way to beat. And in the case of the UK, it's probably exacerbated by that London is not only the largest city, but also the closest large city to Europe, and the seat of Government to boot.