Stable door and bolted horses scenario...

When this whole sorry story started some years ago I had some interesting correspondence with the MD of a company which specialises in stabilising structures, buildings, embankments etc. using very sophisticated grouting techniques. We discussed Silbury in theoretical terms and it seems that a pressurised grout could have been employed to fill any voids within the hill. The grout would have been introduced using boreholes little thicker than a finger and would have been almost identical to the original filling, not exactly of course to preserve the difference between old and new. The grout would have been of the same permeability as the main structure of the hill and would not have introduced any excess water which could migrate and destroy lower archaeological remains.
However, EH were implacably opposed to grouting and I don't know if this sort of option was ever discussed with Skansia.
Ain't hindsight wonderful!
Jim.

P.S. When Winchester Cathedral started falling down in the early 20C, a wonderful thing called "The Greathead Grouting Machine" was used to introduce pressurised cement into the crumbling walls. They were stabilised and stand strong to this day. Did EH even consider that techniques may have improved in 100 years?