finished all the electrics in my kitchen. Have two cables in 38mm wide
capping neatly plastered into the wall. 1 cable is for under cupboard
lighting, the other is for a spur outlet for a cooker hood. Both are
connected to the ring via switched double pole fused units.

My installer (ok, I know it's meant to be DIY, but I was running out of
time doing stuff by myself), despite being given a cable detector and
having the capping outlined on the wall in pencil with the word "WIRES"
written on it, managed to drill a hole right through the middle of the
capping.

AAAAAAAAHHHHHHHHHHHHH!


it looks like the drill may have gone in between the cables and may not
have damaged them. Have checked both cables by connecting stuff to
them. They worked and nothing tripped in the CU. Is there some sort of
test that I can do using my Fluke 89 to see if the insulation really
has been damaged?

Someone said I should fill the hole with silicon sealer instead of poly
filler.

Any thoughts?