That is not at all stupid ! In my opinion there is archaeology to be investigated (in the ditch and they will not look there) meanwhile they should get on with fixing the hole.

While the basic structure is stable - that is to say the original structure - given that one vertical shaft 8'x8' 135' deep has been cut down into the middle (the size of our box bedroom only with lots of head height), one horizontal tunnel cut to the centre from which most if not all the pit props were removed, and another horizontal tunnel cut into this and then the middle which was refilled by compressed air blowing the spoil back in, external slumping - possibly including spoil from the 1776-7 shaft thrown down the sides, plus internal slumps in the 1776 shaft found by those digging the 1849 tunnel, plus slumps and collapses discovered in the 1849 tunnel by the 1968 tunnel, and collapses in this tunnel found regularly at the time....

sorry out of breath with all that digging...

and that EH drilled four- sorry five holes top to bottom to take core samples...

Nigel is right to state it is the integrity of the structure that was always as worrying as a total collapse of the outside breaking inward to fill the shaft. I will only feel easier about that when the hole has been backfilled, and only easier about the tunnels not migrating further upwards when the voids are filled.

VBB