In message
, at
09:47:14 on Tue, 25 Mar 2008, Lüko Willms
remarked:
Comparing just the length of the cross-London tunnel with the length
of the HS1 London tunnel and wondering why the same length of tunnel
can be much more costly to build

Only a third of the Crossrail budget is building the tunnel.

And that tunnel is under random property and roads in Central London.

HS1 is largely built either in open countryside, or under an existing
railway line.
--
Roland Perry