Jack joined us (tunnelling is something he's been exploring a lot in his sandpit at home) and he was soon working away down the mine, eventually coming out the other side.
For safety we made a rule no one down the mine with out a teacher present. To facilitate this Jack decided to board it up when the teachers weren't able to be there. A great idea.
We also said no walking or digging on the top while people were down the mine and discussed not undermining our roof planks. We worked out a communication come emergency breathing pipe for use by our miners.