one should be doubly impressed or more for those that dug tunnels in the prisoner of war camps, considering what tools they had to hand, and their fate if caught, which was to be shot
sure they didn't, however it had to be so covert, the big fear was of being caught, then shot. some did get away, but many who tried and failed were executed.
They talk about silenced pneumatic drill . That's nonsense they can be muffled to a certain extent but it's not just the drills that make the noise it's
the concrete breaking up which creates the most sound . Looking at the fine smooth holes, that was done using using fine diamond tipped drills and there must have been plenty of noise albeit muffled by the fact it was undergound. What is more in the vault there should have been proximity sensors but apparently nothing was detected. I would say they must have had some insider information.