Who's digging the holes?

At lunch today I noticed another van pull up and these guys have started digging a hole in the path with a drill. I was thinking how we never question these people. What if I went out and bought a drill and a van and went round London drilling holes in the street and then never returning? How long before people realised? Outside the Guardian building there are a series of holes that were dug last week and no-one has returned since. Maybe someone has already started doing this...