Thankyou for all the comments. My main concern would be with a Line to Neutral reversal of a PME supply somewhere external to the property (e.g. DNO network), which would not be obvious or detectable by visual inspection during initial verification of a new electrical installation. I am struggling to see how the standard method that an electrician would undertake when checking for correct 'Live' Polarity at the origin (testing L-N and L-E = 230 V, N-E = 0 V) would highlight the problem?

I see what you mean.

I would like to think that the DNOs have a means of confirming correct polarity, but I have struggled to find anything online.

It may not be the advertised process but a wire to any outdoor electrode of opportunity (water pipes, lamp post to the meter probe into the mud, to pry bar or larger screwdriver in the lawn) has been seen being used by the local chaps round here. That and the tip  of a knife to pinprick into the insulation of the cable and then a connection to the knife...

In tight situations when things feel off, folk get inventive quite quickly and SSE are no exception. To be fair the stabbed cable was taped up with self amalgamating tape afterwards, and replaced once the final repair was made.

Actually even the few mm of exposed metal on the  probe tips a digital volt meter makes a good enough "earth" to indicate a few more volts than expected, which is all that is needed to trigger the 'something's up' alert that leads to double checking, It may be an electrode resistance of 10kOhm but the meter still shows there may be dragons.

Mike

It may not be the advertised process but a wire to any outdoor electrode of opportunity (water pipes, lamp post to the meter probe into the mud, to pry bar or larger screwdriver in the lawn) has been seen being used by the local chaps round here. That and the tip  of a knife to pinprick into the insulation of the cable and then a connection to the knife...

In tight situations when things feel off, folk get inventive quite quickly and SSE are no exception. To be fair the stabbed cable was taped up with self amalgamating tape afterwards, and replaced once the final repair was made.

Actually even the few mm of exposed metal on the  probe tips a digital volt meter makes a good enough "earth" to indicate a few more volts than expected, which is all that is needed to trigger the 'something's up' alert that leads to double checking, It may be an electrode resistance of 10kOhm but the meter still shows there may be dragons.

Mike