To add to what VBB has said, and then I'm going to leave it as I'm as irritated as VBB -

Peter, you say -
"Perhaps HA has sought expert opinion from elsewhere and have got a better practical solution to offer."

Have you not understood what we have said all along? There are several solutions. We have merely said, consistently, the most damaging one appears to have been chosen, without explanation. We simply call for a public explanation. What's so peculiar about that???

Your various remarks appear to add up to this:

We are "well meaning amateurs" and perhaps ought to defer to EH else we risk causing a delay. In any event, we'll probably be bamboozled by them so we should "enjoy" the meeting.

Well, as VBB has said, this meeting is quite a slice of history, was achieved at no small cost in effort and should be treated seriosly, not dismissed in a sentence. It may not work, but it's what we've got and it damn well matters.

We are amateurs, but well able to read the documents. Having done so, our strong impression is that tunnelling is NOT the least damaging solution, by a big margin. Perhaps EH will show otherwise, but how anyone can have come to a different conclusion right now beats me. Please explain.

For myself, I feel unwilling to change my tune merely because EH have announced, without the least explanation, that they've decided to tunnel. As it happens, I have very many years of oblique professional experience of structural engineering in the context of collapsed tunnels. Rather more, for instance, than an archaeology doctorate would have given me. Ergo, unless EH do what they've very significantly failed to do despite repeated requests - get REAL experts to say independently and very clearly that tunnelling is the least damaging option then I'm not up for trusting their intentions in the light of my understanding.

As for worrying about further delay, that seems to be based upon a further imperfect understanding of what has been revealed so far. So far as I understand it, and I suspect VBB will agree, the damage caused by the very act of tunnelling is likely to be greater than very many years worth of doing absolutely nothing.

That's what the risk assessment strongly suggests. What would you have us do? Not ask for an explanation?