Hi Telectrix1. outside lights. both L and N need to be disconnected to rule them out.
2.Insulation testing should give high readings, in the MegOhm range, not 0 as your neighbour says.
3.this is not a job for a handman with a miltimeter. it requires an electrician experienced in fault finding with the correct tester/s to investigate.
4. rewiring a "suspect" cable can cause untold damage to decor and you may still have the fault after.
1. Is disconnecting the live wires from the dimmer switches to the outside lights sufficient? If not, what constitutes disconnecting them?
2. I think what he was showing me was voltage.
3. I agree
4. Absolutely this too. I am not thrilled at the thought of this at all. The person I'm caring for doesn't seem to mind so much as long as it fixes it and it is the only solution...but we're both not so sure. I think trunking would be the least damaging solution despite being unsightly.
Is it possible that the Immersion heater, which is on Fuse 3 of the OP photo, could have caused this, despite not tripping? The heater and pump on the same fuse are still working as normal, and the water heater sounds like it's working still (though the water isn't as hot).