In message , at
01:25:23 on Fri, 15 Jul 2005, Nicola Redwood
remarked:
If the reports today (that the explosive was mostly Acetone Peroxide)
are correct, then it would be unlikely given the damage to the train
that any serious damage was done to the tunnel.

Since the rest of us aren't the explosive experts that you are, David,
perhaps you can explain that remark?

http://en.wikipedia.org/wiki/Acetone_peroxide

That explains the chemistry, but says little about what type of damage
it might cause, and why. There were some early reports that the type of
explosive could be guessed from the way that victims' clothes were
"blown off" and other contemporary descriptions of the sound and light
accompanying the blasts. Perhaps these are what were being referred to?
--
Roland Perry