Keep in mind it also has to navigate its way around what’s under London which is a lot more complex than most places, considering it’s full of tunnels, Victorian sewers and mass burial pits.

Less issues if there’s little down there to begin with. Although personally I don’t see why America can’t just build a train like a normal country.

Indeed, if there are administrative overheads of constructing in built up areas then it would be important to compare with a major highway building project also done in or near a built up area.

I’m still left wondering though, in the open countryside, what the complexity (and cost) comparison is between laying down a mile of freeway and boring out a mile of tunnel. It feels like tunnelling is hard and complicated, but so too is making millions of magic coloured tiles that are all connected to each other so we can see each others cats and, very rarely, make phone calls.