Mining in more than one sense; Brave guys indeed and good to see they have not been forgotten.
I can recommend this book if you want to know more in detail :
"The Work of the Royal Engineers in the European War 1914 -1919, – MILITARY MINING" -
Its an official report, so there is much detail into all aspects including Mine Rescue etc. A really good book.
The programme itself was excellent. I do wonder how much more they managed to explore, which wasn't shown for various reasons. I think I would be happier (if thats the right word) exploring the Somme tunnels rather than those in Ypres salient, at least the Somme are dry and not in clay and just importantly not timbered !
It just makes you think, ask your self this question do you think you could have done it ? Not the tunnelling itself but your nerves, the thought that at any moment some one might break in or blow you up. No wonder they drank so much ...
If it can't be grown it has to be mined.