Cabbidges

This is a very genuine question and asked out of fear.

What happens when the next ceiling flood from an upstairs neighbour reaches the point where the mains electricity comes into your house? (UK). Each flood the water reaches a little further, I can't stop the guy from leave his tap running every now and again until my house floods from his overflowing bathroom sink (believe me I'm trying).

To me this seems incredibly dangerous. Anyone with electrical knowledge ...