wrote:
http://www.bbc.co.uk/news/uk-england-london-29520761

I distinctly remember arguing on this group a few years back with someone
saying that walk through tube trains would be impossible because of [insert
nonsense reason about loading gauge here]. Good thing for them I can't remember
who it was and I'm too lazy to go through the archives otherwise there would be
a serious session of I Told You So right now.

Apart from being being lazy, you have a bad memory as well as a poor grasp
of engineering. The argument was with me, and it was that small-size Tube
stock would need to be articulated to have wide through gangways. Years
ago, such trains were proposed for the Victoria line, but Metronet went for
cheaper conventional stock with your favourite thick walls instead.