You know when you're doing DIY and you accidentally drill into a mains wire?

Ooops!

To be honest, I am only surprised that it doesn't happen more often around here. I remember going to Brentford High Street a few years back to speak with contractors who seemed to be continually expanding the area that they were working on, and it got to the point where there was barely any road left. The site foreman was really good about it, and even took me into the works area to show me what was going on - essentially, their task was to find and replace a water pipe, however the more they dug the more a maze of pipework was being uncovered - the vast majority of which they knew nothing about, and had no idea if it was in use or even connected to anything.

More recently, I went to an excavation to repair a collapsed sewer - when they dug the road up they discovered a massive cast iron chamber with pipes leading in and out in all different directions, and it was deep with a capital 'F'; took them two months to engineer a suitable solution, and to this day they still can't be sure that they have got everything that should be connected actually connected.

There is loads of stuff under London roads that nobody is aware of.