[Beardyman]

Probably one of the worst/dangerous ones I've seen was when I was helping a friend renovate his house. All the old wiring had to come out & I found, just under a floorboard, the downstairs socket ring which had been spliced. Not an issue in itself but whoever had done it had simply twisted the wires together then insulated with sticky tape. This was then put in a notch they'd cut out of one of the floor joists. Apparently when he'd had the electrics checked they'd found a live/neutral/earth problem which they couldn't pin point & advised the best thing to do would be to re-wire throughout. Looks like I'd found it by accident.