@Murdoch , I think you were a bit harsh on the electrician in this instance and made no comment on the incompetence of the meter installer who’s job it is solely to check polarity, fit a meter and check polarity again.
Just my opinion but. . .
Mmmm,however,this is the dude who did not practice safe isolation,where he should have...and he would have still,found the issue.
As for the meter fitting,i despair... i am prepared to believe some of these Hunger Games bit-part players,could find a "third way",to connect two conductors.....like those M C Ischer drawings of cricket stumps with two at one end,and three at the other...
I did a post,a while ago,regarding one such fellow...he got indignant,in the extreme,as i suggested he needed a 4 pole isolator,in the fitting of a RHT meter,replacing two old,separate meters.
He repeated 4 times,how it would not work,as it would "short".
Eventually,and with the most patience and manners possible,i drew him a wiring diagram,with a child's felt-tip pen,on the side of a cardboard wine box,in the garage...He had an actual,not a metaphoric,face-palm moment,and asked to tear the drawing off the box,and take it with him.
The above incident formed one payment of compensation,out of four,to the owners,by the supplier...