Plans get lost, stuff gets bricked up, there were a number of bombs fell in that area during WWII (http://bombsight.org/?#16/51.5187/-0.1039), it can mean expensive surprises when doing building work.
When they were building the Eurostar tunnels down the road from me they found a load of disused wells that nobody had any idea existed, with unfortunate results.
Plans get lost, stuff gets bricked up, there were a number of bombs fell in that area during WWII (http://bombsight.org/?#16/51.5187/-0.1039), it can mean expensive surprises when doing building work.
When they were building the Eurostar tunnels down the road from me they found a load of disused wells that nobody had any idea existed, with unfortunate results.