"FWIW, I think it would be a waste to not try and use the tunnel that is there to gain more insight into Silbury."

More evidence you don't know the first thing about anything.

Which tunnel?
The one that's 50% entirely collapsed and 50% migrated up from where it was because of partial collapse?

And how will you use it, when the reboring will be bigger than the original and so utterly destroy it?

So your proposal is to use a tunnel that is half not there and half elsewhere and will be then entirely not there, for research?
Good trick.

No you don't know your stuff. And no, I'm not pointing you to the literature. Read it yourself and come back another time. I'm bored with this thread.