Peter Parry wrote:

He also took 9 x 4mm (single) conductors down from steel trunking
through a hole he cut with tinsnips and left with razor sharp edges
without fitting any grommets and to get from one side of a room to
another used the convenient trunking carrying 40 data cables to put

Possibly there is special training involved to ignore any grey
(or white) cables already present. It's a pity no-one appears to
make trunking with "no mains" printed all over the inside.

his ring main wires in, he did tuck them neatly under the Cat 5
cabling though.

That's so that if someone complains he can claim that his wires
were in there first. (Thus it's someone else's fault for putting
the data cables in with the mains.)

Qualifications are no measure of competence or quality of
workmanship.