What is it with some people that makes them think that the most attrocious wiring is O.K. if it's "only" feeding a shed or garage outside?
Call for a main RCD tripped and wouldn't reset. I traced it to a ground fault on the main ring then started to go around unplugging everything to determine whether it was an appliance or the house wiring itself. Didn't have to go far before I found the culprit, a DIY hack installed to take power to a shed and garage.
This "quality" installation consisted of a 4 sq. mm T&E cable jammed into a regular BS1363 plug and shoved into a socket in the kiddy's bedroom. Sheath stripped right back since there was no way it would go into the cord grip, of course.
The cable ran loosely along the baseboard, across a conservatory and then through the outside wall where it dropped straight down into the ground. Somewhere a few feet away by the fence it went into plastic tubing, but the section from wall to fence was just buried directly in the soil.
At the shed was a regular round 30A junction box, splitting the circuit to a double socket and to an SWA cable which disappeared through the shed floor to go across to the garage. No cables fixed, no protective grommet on the metal backbox, sheaths stripped back so far on all cables that inners were exposed for at least a couple of inches, sometimes much more. The earth to the SWA was just a couple of strands of the armor into the terminal on the box.
The other end of the SWA emerged in a greenhouse attachment behind the garage, hung loose with a big loop for a couple of feet in there (why?) and then went through into a double socket. I didn't even bother to open the latter, but all plastic, no gland, so probably just a couple of armor strands straight into the earth terminal.
And you know what? The guy that did this couldn't see that there was anything wrong with this mess!