The existing setup: A lounge with one ceiling light controlled by one wall switch. Cables are twin & earth.
What I want to do is run a cable from the *ceiling rose* in the lounge to an existing light switch in a hallway leading off from the lounge.
I then want to replace the hall switch with a dual-gang switch. I want one side of the new hall switch to control the hall light, and the other side to control the lounge light. The original lounge switch must behave as before: switching the lounge light on and off.
I'm guessing this is dead simple to do, but would be very grateful for a link to the relevant wiring diagram, or alternatively, worded instructions. Thank you in anticipation...
An alternative solution would be to run a cable from the lounge ceiling rose to a second single-gang switch in the same room, so each of teh two switches in teh room can then turn the light on and off.