When working in my loft last weekend I slipped while drilling and the chuck (not the drill bit) caught a lighting cable sleeve. The outer sleeve has been penetrated and the cables are visible underneath (I can't see copper but the inner sleeve is slightly damaged). My conservative instinct says replace the entire cable junction box to junction box, my more laissez faire side says use insulation tape to wrap the damaged area, the middle ground would be to cut the cable where it is damaged and insert a junction box.
I understand that if I was talking about a cable carrying a higher amperage (e.g. a supply to an electric shower) then I would need to replace the whole cable, but my instinct is to cut the cable and drop in a suitable junction box because there is slack in the cable.
What are the educated views on this point and is such work part P notifiable?