A piece of brown sleeving is used on the blue wire as both wires are live. It is absolutely vital that the terminal screws do not clamp on the insulation of the cables.

One Way Lighting Circuit Modified For Two Way Switching
Wiring a light switch one way. Wiring a single pole light switch here a single pole switch controls the power to a light fixture. One wire connects to com and the other wire to l1. The white or neutral wire bypasses the switch and goes straight to your lights. Wiring a light switch with the power coming from the light s to the switch is probably the easiest way to wire a switch. One way switching metal switches as with the plastic switch. Connect the new socket or switch as shown in the appropriate wiring diagram in these fitting instructions taking care that only the copper conductor s enter the terminals.
The source hot wire is connected to a switch terminal and the other terminal is connected to the black cable wire. The earth wire connects to the earth terminal on the switch plate. The switch serves to cut the power from reaching the light switch. A one way light switch is quite easy to wire up. If you have the chance wire your lights this way as it is the easiest scenario. The red wire from the feed cable is connected to the top terminal the red wire going to the light is connected to the bottom terminal the black wires from both cables are connected together in a plastic terminal block and the earth wires are connected to the earth terminal.
How to wire a one way lighting circuit in this tutorial i show how to wire a one way light switch i show how a 1 way and 2 way light switch works i explain how to wire a ceiling rose how to. A standard single pole light switch will simply require you to attach the black load wire into it and then the black wire leaving the switch and to your lights. The cable going to the light switch is connected as follows fig 2. The source is at the switch and 2 wire cable runs from there to the light. In your switch box you will only have one black one white and one ground wire.