I'm not sure about the Ravers. It's possible I suppose but I have seen ropey jobs carried out by so called professional DNOs. Particularly with older cable excavations.
I'll grant you it does look odd though.
one of our course delegates claimed that a few years back he worked for a company that suddenly found the factory had no electricity, apparently they'd been wired into the mains (possibly from the street lights) bypassing the meter, it was only the power to the office that was being paid for. The council were unhappy apparently.
I expect the cabling for that wasn't done properly
The reason I mention it is that it looks very similar to the cable I laid for the lights in my decking, while hungover to **** one day.
How big is your decking if you need 415v powerline to it?