[xioxox]

What's the good of a perfect railway line if it never gets built? What happened to the capacity argument? There is likely a good optimum between the cheapest and most expensive possible for capacity and speed. We could all fly around in supersonic aircraft, but there's a reason we don't.

[pjc50]

It's getting built! Large sections of it are nearly finished!

Quite a lot of the cost is the NIMBY appeasement mentioned upthread. Something like a quarter of the line will be in tunnels. Making a slower line wouldn't make that any cheaper.

[glompers]

Connections to HS1/Europe, and to Leeds, Golborne, East Midlands, Manchester and finally even Crewe have all been cancelled so now extra expenditures will focus instead on Euston Station. That's not the large section people were interested in riding. Perhaps Old Oak Common should instead have been tunnelled the same distance through to Waterloo International (whose international platforms are now deleted).