Chris

No time to re-prove the 2 pole voltage tester as he was on his way to hospital in an ambulance.

The other suggestions were worth considering but not the cause.

MAPJ was the closest for the explanation.

A couple of months earlier a contractor for the meter operator came and swapped out the supply meter.  He connected the meter reverse polarity. So now switching off the MCB switched off the neutral.

There was no continuity on the CPC to the ceiling rose.

The 2 pole tester was of the type that needs to see a potential difference between the probes and did not gibe a warning of the presence of a live conductor with only one probe connected. I have a collection of a range of 2 pole testers. Some do not give a "one handed" probe warning even from the same reputable manufacturer. With no CPC continuity and the neutral isolated the 2 pole tester could not "see" a potential difference.

Make sure your 2 pole tester does a one handed test for live or drop it in the bin and but a new one.

So make sure your 2 pole tester does give a one handed warning. Also as I have said, keep a good quality volt-stick tucked in the top of your shirt and use it before touching anything conductive.  The Kewtech dual voltage non-contact tester in my view is the best there is on the market as it indicate live if it is anywhere near live and then press the button to desensitize it to  to identify individual live conductors.

See the IET Guidance Note 3 and The Electricians  Guide to the Building Regulations for their recommended procedure for safe isolation and the last step for identify lost PEN conductors. 

I wonder whether Colin sued the meter company?

2 faults in the installation!

I suppose that whoever put in the ceiling rose with a 2-core flex to the lampholder did not find it necessary to check the continuity of the CPC.

Isn't the other important point about proving dead that it only proves it there and then? I had wondered about a borrowed neutral and another occupant turned a device on just afterwards, or even a timeswitch operated. Ideally, the main switch should have been opened, but the wife was doing the cooking, the kids were watching the telly, etc., etc.

I wonder whether Colin sued the meter company?

2 faults in the installation!

I suppose that whoever put in the ceiling rose with a 2-core flex to the lampholder did not find it necessary to check the continuity of the CPC.

Isn't the other important point about proving dead that it only proves it there and then? I had wondered about a borrowed neutral and another occupant turned a device on just afterwards, or even a timeswitch operated. Ideally, the main switch should have been opened, but the wife was doing the cooking, the kids were watching the telly, etc., etc.

Chris

Substantial damages from the meter operator for their negligence, his injuries and time of work and loss of earnings as he was a self employed electrician. He did not tell me how much but I think it was a significant sum.

JP