I had a domestic job a couple of summers ago in a bungalow. Outside lighting problem lead into new 1.5mm black flex into the loft into the new PIR then off to the lights via a contactor (DIY job before). I had to crawl around the loft pulling the new flex in while trying to find the old feed. Track it to a jb then off to some 1.5mm t+e to a spur in a back bedroom. So we asked the owner if we could go in, in broken English he said can we come back tomorrow. No problem off to a couple more jobs and came back the next day. In that room there was a small Cannabis growing plant. I suspect that what it was

No idea what was there the day before when he asked us to live. Was a little shocked. I Finished and walked off. The guy I was working with just sat outside deciding what to do.
We never even got paid for the job.
Edit: Was asked by a mate to have a quick look at his parents alarm system. Big house even had zone expanders. While finding the fault I had to find the zone expander on the new extension (4 rooms, kitchen, attic). This was in the back of a big walk in wardrobe. Me and a mate of mine I drafted in who was good with larger alarm systems gave me a hand. So with no lighting in this wardrobe (second job to do there) and we could stand in it we started to get the floor up (suspected cabling fault). Armed with 110V site lights.
A little busy with the job and in a rush we never look around us. We got the floor up in the dark. So we find the fault put the floor back down. Put the zone expander back together and look around.
We see bondage gear, chains, whips all around us. This is my mates parents house who I had known for years. We panic. About to leave and my mate walks in with a cup of tea. Looks inside his parents wardrobe to see where the fault was and asks us to promptly to leave.
Then we notice the big solid metal welded bed and it all made sense.
Never spoke to my mate much after that.