I am familliar with the loop-in system of wiring lights, and with the old junction box system. However, I have recently replaced some ceiling rose and pendant light fittings for my dad. With the loop-in system, you get three two-core and earth cables (or two if it is the end light), and if it is a junction box circuit, you have one two-core and earth. However, what I found was two two-core and earth and a single core cable. Also, I isolated the circuit by turning on the light then turned off the MCB which turned off the light, just to be sure that I turned the right one off (it was the landing light, and I didn't know if it was supplied by the upstairs lighting circuit or downstairs.) The downstairs lighting MCB turned off the landing light, so I assumed it was isolated. It was not, as I found out later. So, what type of wiring is this, and why las it still live after it was supposedly isolated?