Worst ? ..no, quite often find substandard work similar to this. Builders, kitchen fitters, diy bodgers list is endless, everyone ones a spark, after all as long as the light comes on or the socket works who cares a ----, certainly not the customer. This type of work is usually price driven or on rare occasions customer's ignorance or a rip off.
He may have 10 years experience but he is a danger to himself and the public. This country is not investing in our youth, who will be tomorrows electricians, plumbers, gas engineers and the like. I shudder to think what the level of competency to expect in 20 years time when the chickens come home to roost.