Finally got round to looking at the upstairs lights in this place, and discovered that all the chased-in cable uses 15mm copper as conduit containing 1 or 2 1.5mm cables (well, could be 1.0)

My understanding is that this doesn't need earthing (it isn't) because it contains normal T+E, so double insulated.

My concern is that when I pull new cable through it, I run the risk of damaging it, particularly if I'm running two cables. I can deburr as much as possible - it's already deburred - and tape over the edges - but is there anything else to help matters?