In message , at 20:24:40 on Thu, 4 Jun 2015,
Mizter T remarked:

HS1 ate someone's back garden in the Stratford area.

Which is just wot I said in my earlier post!

Ah. Yes. But "tunnelling collapse" doesn't always produce a sink hole.
The Crossrail one for example.

But there was another in the middle of Heathrow when they were building
HEx (with the same sort of sprayed concrete design as Crossrail).
--
Roland Perry