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Deleted member 26818
Sorry, should have mentioned the CSA of the conductors for the lights on the stairs is 2.5mm2.1 - C2
2 - C1
3 - C3 if all plastic, C2 if any metal.
Obviously 3 was a C2 as the face plate was live.
During the course of my testing I de-energised and re-energised the circuits a few times.
Though I did remove the C1 first.