Tiling over a back box

It should be identified and cut off at the other (source )end in such a manner that it can't be reconnected. Then it doesn't matter what you do.

That's the ideal solution, but TBH it seems a bit OTT to me (unless it is easy to do). Since it's not carrying load, surely you don't need choc bloc screws to be accessible. If it were me, I don't think I would even use a proper blanking plate; I'd put a bit of tinplate or ally inside the box, and flush tile over the lot. Assuming the circuit is on an RCD, there's virtually no risk to anyone who hits the now completely concealed wire with a drill or nail. I guess if it was in a "location likely to be drilled in future" I would keep the blanking plate.

At the supply end join all the wires in the cable together and connect to earth; sleeve and label accordingly.

Likewise at the back box end common them together and connect to the earth terminal on the box.

This prevents the cable becoming live inadvertently as if it does the protective device will trip.

Then tile over the box with a pretty tile that meets Management's aesthetic demands.

Owain

Many thanks for the suggestions.

That does sound the best solution, and did have in mind labelling the source end accordingly.

I would strip the outer sheath back a couple of inches, leaving the insulation on the live and neutral wires. Then cut all the conductors off at different lengths, fold then back onto the sheath and tape round the whole lot. Nothing bad will then happen, whatever happens to the other end of the cable.

Rather than a blanking plate, cut a piece of hardboard to be a tight fit

Wouldn't it be safer to join them together in an insulated connector and not connect them to the box? Then if some fool connects the live before connecting the earth at the supply end nothing will become live (like the box and wall).

If you can find the supply end, why not just disconnect and hack off where it enters the CU?

If you know where the souce end is then just cut both cables back as far as you can so that they cannot be reused and fill the backbox with any old s**te you like and tile over it.

Does s**te form a firm enough substrate for tiling?

NT