I'm not sure that insisting on bringing a CPC to places where one is not required is always the best approach. I guess this can be used to verify RCD operation by introducing a fault to order whenever  the light is switched on, or maybe the other end is not earth at all but is some cunning way of feeding power in a daisy chain to another location.

by a very small margin, I'd  prefer to see that CPC cut back.

(really it should end neatly in a choc bloc single, or a wago or go under the head of one of the back box  mounting screws. Flapping free  sleeved but folded to a hairpin so the sleeving stays on also works if done well.)

M.

I favour 3 core cable with the grey sleeved with the g/y sleeving to give anyone looking to think about it.

That's my story and I'm sticking to it!

Ooh Norman lad, complicating it even more for the hard of thinking, is that a good idea or are you imagining it might kickstart them to actually think? 

I've seen the c.p.c. reused as a live before- usually where someone tried to convert to 2-way switching but didn't want to disrupt the decor by changing to a triple and earth. I wonder if the switch was a 2-way one in a previous stage of the installation's life and then converted back.

   - Andy,

Either - it is single red and earth, Or, the black has broken somewhere and the cpc has been utilized as a replacement!