Not sure why you are calling the top switch in the diagram the 'third', but ok.Guys, here are the two switches on my landing. Third switch is downstairs. Looks like I have fed my new cable to the third (top) switch in the diagram and not the intermediate.
Nearly all cables have "a neutral coloured wire" - that does not mean it is being used as a neutral.Difference with my switch to the diagram is I have two neutral coloured cables terminating together too...
Can we have a better picture of the switch to show this and so that we can see which cables the wires come from?