Domestics...

[SUNRAY]

I remember looking at a compressor, using my multi-meter on ohms, and reading seemed OK, but returned with my mega and it showed short circuit. If multi-meter not showing infinity, then likely a fault.

Yep 400KΩ is not enough to trip the RCD but didconnecting the blue neutral leaves the RCD holding ok. I fully expect expect a very different reading using insulation tester.

If you had not showed the switch drop, I would have said three core used for that,

Twas my instant assumption until I started unpicking the bundle. I was hesitant to do so but the other downstairs lights are horrible Ikea stuff and ba****ds to fit so I avoided touching them which thankfully proved to be the right move.

 

[ebee]

I would be looking at the lights in the adjacent rooms to see if the connections are similar or offer up any clues

Strangely enough I mentioned to an electrical pal about half hour ago that some folks get the notion if an electrical circuit is not a bog standard electrical circuit it is therefore incorrect, irrespective of whether it actually is incorrect or non-compliant

 

[sparkwright]

Strangely enough I mentioned to an electrical pal about half hour ago that some folks get the notion if an electrical circuit is not a bog standard electrical circuit it is therefore incorrect, irrespective of whether it actually is incorrect or non-compliant

Yes, it's not necessarily wrong.

I seem to remember adding some lights in an unconventional manner to avoid loads of trunking - by taking the live from the light switch, and the neutral from the emergency light supply (single pole key switch). So that meant running cables with one conductor (and earth).

Naturally, a few years later the maintenance guy decided to change the new lights, and wired them how HE thought it should be, because it 'didn't look right' how I had.

Bastards.

 

[SUNRAY]

Yes, it's not necessarily wrong.

I seem to remember adding some lights in an unconventional manner to avoid loads of trunking - by taking the live from the light switch, and the neutral from the emergency light supply (single pole key switch). So that meant running cables with one conductor (and earth).

Naturally, a few years later the maintenance guy decided to change the new lights, and wired them how HE thought it should be, because it 'didn't look right' how I had.

Bastards.

I've even known something similar logged as C2 & C1 along with the quotes to make it safe.

It breaks my heart to see the public being abused by some of these Bastards.

EDIT: I've known wiring and conduit on a farm being ripped out and replaced with larger tube because the live and neutral entered from opposite ends

 

[ebee]

The age old "Two circuits on one fuse" used to be pretty rife as a fault determination by some .
How the hack can it be?

Similarly the two rings on one fuseway crops up often (well everytime I mention it anyway = ooh I am a devil I am), Anyway it all adds to the fun.
Just to note - No normally I would not advocate two rings on one fuseway anyway but to condemn it as non compliant or dangerous is something different.