Busy renovating a terraced house. This weekend I started removing some blown plaster which soon became removing all the plaster. The browning is still on the wall and in the top corner I noticed a crack in the browning. Had a closer look and found that it was a mains cable that runs diagonally down the wall from the top right corner to a two way socket about 4 foot in from the corner. The cable is plastered in and it's a good job I didn't try to knock in any nails anywhere on that wall. What's the best option?