Thank you for all that. I was familiar with circuit box system and with looping in at the Rose. I was not familiar with looping at very crowded switch box.
I was hoping to identify the supply to a lighting point from the fuse box using a detector pen and switching on /off at the consumer...
I am installing a new light in a converted loft area.
There are plenty of wires at 1.5 and2.5., but there are no junction boxes and no convenient ceiling roses.
I was proposing to cut into a 1.5 cable and install a junction box from which to run a light supply wire an a switch wire.
How do I...