On 10/11/2020 02:46, williamwright wrote:

It's difficult to do this, and you risk damaging the plaster worse than
cutting it. I always used to cut a slot in the plaster. It needn't be
very big and with a bit of skill you can disappear it with polyfilla and
sandpaper. Have you considered dropping the cable somewhere where a cut
in the plaster wouldn't matter, then running it horizontally?

And adding a blanking plate where it turns the corner to comply with
requirements for permitted zones
http://wiki.diyfaq.org.uk/index.php/...lectric_cables