The coroner observed that the cable was only 10mm deep in the wall insted
of
50mm. Have the regulations changed? I don't think any cables in my house
are
sunk that deep.

It is an either/or thing, which the report doesn't make clear.

Your choices:

1. Bury 50mm deep (so nothing reaches the cable)
2. Run in prescribed locations (fitter knows not to drill above sockets
etc.)
3. Provide mechanical protection (so the drill blunts itself on a metal
casing)
4. Surface run (so you can see where it is and avoid it)

Personally, I don't think 50mm is enough. Drilling for a rawlplug will
frequently go deeper than this. I tend to use brown plugs and 60 or 70mm
screws.

Christian.