Switch wire. 2 of 3 are live!

[Riki]

So at R1 you have definitely made sure which black is the switch wire.?
With the power off checked which black has continuity when the switch in that room is on, and then open circuit with the switch off?

Edit: That is testing between the 3 reds and individual blacks.

Absolutely.

 

[securespark]

Same results. Switched live to earth 246V and neutral to earth 246V

That should be zero.

Unless that "neutral" is a switched live or it is an open circuit neutral.

If the switch is closed in this diagram and the neutral is open ended, it will become live.

http://inspectapedia.com/electric/0507s.jpg

 

[endecotp]

Switched live to earth 246V and neutral to earth 246V

Neutral to earth should be essentially zero.

Something is wrong. I don't think the problems can only be in that light fitting; to get those results there must also be a mistake elsewhere.

Earlier you mentioned that a lamp flashed when you toched it. We don't know why that is yet.

If I were you, I'd disconnect everything and start from scratch by working out which cable goes where and then re-connecting one wire at a time and testing each connection as you make it.

 

[Riki]

I have disconnected and reconnected both R1 and R2 several times but failed to solve the problem. I am now taking a break and shortly on holiday. When I come back I'll call an electrician and report the outcome. You can't win them all! Thank you everybody for your help and patience.

 

[Riki]

Fixed! It took the electrician well over an hour to ascertain that the culprit was a loose/disconnected neutral in a junction box "somewhere" (it baffled him for a while). He didn't bother to find out where the loose wire was and instead connected a NE cable between R1 and R2.The job was finished in over 2 hours. Phew!