I had to chuckle at Overlander's picture. In 1990 just after the iron curtain opened, I was in Warsaw for the first time. I saw a scene like this during the replacing of paving slabs along a pavement. 10 men were standing watching one man work. In my prejudice (reinforced by staffing conditions in a lab which I visited on my business) I assumed that this was because labour was very cheap and everything was very inefficient.
When we walked back past the pavement workers after a dinner in a Polish restaurant (after a dinner during which the performance of the waiters confirmed my suspicions about inefficiency and over staffing), a really long distance of pavement had been replaced but there was still only one man working with 10 watching.
Perhaps in Overlander's picture each man will work in the hole for 3 minutes in an hour at very high output and the whole job will be completed in the space of a few hours. What a contrast with the water board near my house before Xmas when a cracked main took 4 days to repair with two or three men appearing for short intervals over this period, and doing a bit of digging to find the split and leaving with numerous traffic barriers etc distrupting traffic. Then leaving with barriers in place for another team to arrive to do the tarmac repair.
Our inefficiency these days is a beyond a joke with road works left in place for months and no one working 24/7.