On a recent job to fit a TP meter, i went to the local site isolator, turned it off and walked back to the site and low and beyond the power was still on...... opened the isolator cover to find exactly what the OP had.
I , a bit like the OP, not easily disturbed but i was so surprised to find ANYONE would actually wire an isolator that way that i could not rest until i had formally informed the duty holder, got him to confirm all site electricians were aware of it and begged for it to be sorted, unfortunately the whole extended site needed to be turned off as the incoming tails were feed from main busbar. Anyway all sorted and i managed to fit the meter, .........